The struggle for the GOP Presidential nomination remains wide open and lavishly unpredictable with no front runner or clearly defined contours. Any one of five candidates could become the party's standard bearer -- Romney, Rudy, Huckabee, McCain and even Thompson. Even long-time skeptics now acknowledge the very real possibility (that I predicted some six months ago): that these contenders battle it out inconclusively for more than six months, continuing the contest all the way to the convention in Minneapolis, with no candidate commanding a clear majority of first ballot delegates.

Meanwhile, as the nation waits for a Presidential nominee there's an increasingly obvious choice for the Vice Presidential nomination, based on five iron-clad and important Running Mate Rules. Whoever wins the top spot on the ticket should pay close attention to the record of recent campaigns and select the inescapable candidate based on these undeniable principles:

RULE 1: FAMILIAR AND REASSURING BEATS NEW AND "EXCITING"

The most successful running mates of recent years were well-known, highly respected senior statesmen -- not newcomers or rookies. Lyndon Johnson (who ran with Kennedy in '60), George H.W. Bush (who ran twice with Reagan), Lloyd Bentsen (who helped Michael Dukakis as his running mate in 1988), and Dick Cheney all re-assured voters that their relatively inexperienced standard-bearers would benefit from their sage counsel and extensive experience. LBJ had already established himself as the most powerful man in Congress as Senate Majority Leader; GWH Bush, Bentsen and Cheney all boasted a combination of both Congressional experience and prior service as major cabinet level officers. At the other extreme, whenever Presidential candidates attempt to add "excitement" to the ticket by selecting little-known "fresh faces," it ends up as an exciting, fresh-faced flop-- often sealing the ticket's defeat. When Dwight Eisenhower picked the youthful newcomer Richard Nixon (only 39 years old) in 1952, the Nixon Fund/"Checkers" scandal almost forced him from the ticket. Goldwater's selection of obscure, upstate New York Congressman William Miller (father of today's leftist radio talk radio host Stephanie Miller) to run with him in '64 only cemented the public impression of the Arizona Senator as a hopeless fringe candidate (he lost in a landslide).

Nixon tried to startle the political world by boldly selecting a freshly-elected Maryland governor with a "funny name": Spiro T. Agnew. Not only did this surprise package quickly blow up in his face (Agnew’s odd comments and gaffes plagued the whole course of campaign '68) but Spiro T. was forced to resign in the midst of the second term on corruption charges dating back to his Maryland years. Geraldine Ferraro (another unknown Congress-person from New York) provided no help at all for the Mondale campaign in '84, and the sad experience of much-reviled Dan Quayle (meant to mobilize voters of a "new generation") in '88 and '92 remains fresh in the nation's memory. For the last quarter century, candidates appear to have learned this lesson: it's the job of the top of the ticket to generate excitement or to offer the prospect of freshness and change, and if the main guy can’t provide that spark it’s foolish to expect magic from the running mate. On the other hand, a grey eminence in the style of Cheney can only make the top guy look more vital and thrilling by comparison-- and reassure people that the VEEP's ready to go in a national emergency and a transfer of power, the last time that anyone's hungering for excitement.

RULE 2: OLDER IS BETTER THAN YOUNGER

Whatever his faults and fumbles, Cheney displayed the key advantage of an older, accomplished Vice President: he never waited on deck as a potential successor, or maneuvered to secure his own future. A Veep who's not a possible Presidential candidate himself has far less temptation to upstage his boss, avoiding the sort of problems that regularly characterized the Kerry-Edwards team in 2004. New reports on their relationship indicate the damaging impact of Edwards' obsessive concern with his own image and prospects, and his refusal to perform the tasks or to advance the themes the campaign leadership assigned to him. For the Presidential candidate personally and for the nation at large, there's something vastly reassuring about an older Vice Presidential nominee whose only interest is service and support, rather than plotting his own future races for the top job. With our long, punishing nominating process, no Presidential candidate can ever come across as Olympian, detached, unambitious, or unselfish, but those look like admirable qualities in a second banana. The chances are that any Republican nominee (except the 72 year old John McCain) and any Democrat (except the 123 year old Mike Gravel) will choose an older running mate this time.

RULE 3: FOR PRESIDENT, WE LIKE OUTSIDERS, BUT FOR VEEP WE NEED AN INSIDER

In the last thirty years, all the most successful Presidential candidates have been governors (Carter, Reagan, Clinton, George W. Bush) who promised to come to Washington as outsiders who would clean up the mess. But for an even longer period all Vice Presidential candidates have been insiders with many years of inside-the-beltway experience. Since 1948, in fact (when California governor Earl Warren won the VP nomination alongside New York governor Tom Dewey) every since Vice Presidential candidate nominated by the conventions of either party has served time in Congress—an astounding string of 28 running mates in a row who served in Congress, rather than as governors or mayors or generals or business executives. (Just to fend off nitpickers—in 1972, George McGovern initially picked Senator Tom Eagleton of Missouri as his Democratic running mate, and the Democratic Convention nominated him. But after revelations about his psychiatric hospitalizations, Eagleton withdrew. McGovern then picked Sergeant Shriver – brother-in-law of President Kennedy, father in law of Arnold Schwarzenegger and very much a DC insider) as his substitute running mate.

Technically, though not nominated by the convention, Shriver counts as the only Veep candidate in 60 years without Congressional experience). The reason that “insider” status has become a virtual requirement for a running mate is obvious: we all want a Vice President who knows Washington well enough to step into the job at a moment’s notice. We assume that a governor who’s never spent time in DC will get a chance to learn the ropes as he gradually settles into the office, but a Vice President forced to take office after the death or incapacity of his predecessor never gets that chance.

RULE 4: IF POSSIBLE, CHOOSE A RUNNING MATE WHO’S RUN A PRIOR, CREDIBLE CAMPAIGN FOR THE PRESIDENCY

The big advantage in choosing a Vice Presidential nominee who’s run before for President is that the candidate has already been vetted – whatever skeletons he (or she) may have kept stashed in the closet has already been discussed and digested by the press. The VP candidates plagued by scandal or controversy regarding their prior careers (Nixon, Agnew, Eagleton, Ferraro, Quayle) are those “new faces” who’ve never run for national office before. Reagan and Kerry both selected runners up as running mates: George Herbert Walker Bush and John Edwards had both fought hard and effectively for the Presidential nomination, enhancing their national stature and providing a chance for the media to sort through any embarrassments. Bill Clinton and Bob Dole both selected running mates who had run prior races for the White House: Al Gore and Jack Kemp had contested for their respective parties’ nominations in 1988. Selecting a previous Presidential contender provides a Veep candidate who’s already built up relationships with the national media and the people at large, and will harbor few nasty, unexposed secrets (like psychiatric hospitalizations or bribe-taking in Baltimore).

RULE 5: ETHNIC, RELIGIOUS OR GENDER NOVELTY DOESN'T MATTER

With mainstream media fixated on various “firsts” in the Presidential race (first woman, black, Hispanic, Mormon, and Italian American double-divorcee as serious candidates) there’s a natural tendency to look at other “breakthrough” possibilities in a running mate. Any smart nominee will resist this temptation: whenever it’s been tried in the past, it’s always failed. In 1984, Walter Mondale supposedly “made history” by choosing Geraldine Ferraro as his running mate; they then proceeded to make a different kind of history by losing 49 states. Sixteen years later, Al Gore got huge publicity for selected the first Jew (and first non-Christian of any kind) in Joe Lieberman, but despite the praise for his choice they lost an election Democrats should have won. It’s possible that a few extra Jews voted for the Democratic ticket because of Senator Joe-mentum, and that might have helped in the startlingly close race in Florida. Nevertheless, even without a Jew on the ticket the Democratic candidate (John Francois Kerry) still drew 74% of Jewish voters (compared to 86% for Al Gore). Barack Obama’s current difficulty in getting a majority of black voters to back him against Hillary indicates the folly of assuming that voters will back your ticket based on ethnic loyalties.

Republicans should therefore avoid the trap of believing that they must trump some “breakthrough” nomination by Democrats (Obama, Hillary, Richardson) with some breakthrough of their own. Finding a black or female or Hispanic running mate won’t automatically boost the GOP in those communities. At one point, the party establishment spoke longingly of Condoleezza Rice as a running mate and fantasized about her ability to compete for both black and female votes. Her controversial tenure at the State Department, however, and her association with both Iraq War problems and a misguided “peach process” for the Palestinians, makes her unthinkable as a Vice Presidential candidate. Ethnic or religious identity will matter for a running mate in 2008 only in the long-shot event of Mike Huckabee winning the Republican nomination. If he does, he must reach out to a non-Evangelical – a non Protestant, in fact – for the second sport on the ticket. That balancing act would be essential in this special circumstance to convince the country that despite his background as a Baptist pastor, Huckabee’s open-minded, tolerant, and respectful of other faiths. In the unlikely event that he grabs the top sport on the ticket, he must choose a Catholic, a Jew, or even a Mormon to demonstrate that the Republican Party hasn’t been captured by a narrow cabal of religious zealots.

With these commons sense, unassailable rules in mind, one potential choice for the Vice Presidential nomination should emerge as an apparent Veep frontrunner – and his name is John McCain.

He conforms perfectly to all four rules – he’s a well-known, nationally respected figure, hardly a fresh face; he’s a septuagenarian candidate who won’t be plotting his own future races; he’s a Washington insider (and easily the most influential single Senator of the last twenty years) who certainly qualifies as a hard-wired insider; he’s run for president twice, maintaining his dignity and integrity on both occasions; and his selection hardly qualifies as a “stunt” choice meant to grab votes in some sub-group (Episcopalian war-heroes hardly count as a contested voting block).

Some may object to the idea of McCain as a running mate because his record (particularly on campaign finance reform and immigration) won’t match the position of the nominee. Aside from the fact that he’s changed emphasis on the issues (he scarcely speaks about campaign financing and now insists on “border security first” regarding immigration reform) history shows that issues disagreements never hurt a ticket. No one looks closely at a Veep candidate’s position papers because it’s obvious that he won’t be shaping policy. Kennedy and Johnson, Reagan and Bush, Gore and Lieberman all disagreed on crucial issues, but media and voters ultimately ignored those disputes – especially after the Vice Presidential candidate inevitably (and appropriately) signified that he would follow the President’s lead.

Given the non-existent foreign policy and defense experience of the three front-runners (Romney, Huckabee, Giuliani) a McCain choice would be particularly necessary – sorry, Rudy, serving as New York City Mayor and responding to local destruction doesn’t truly amount to leadership on foreign affairs (however admirable it might be). Moreover, McCain’s home state, Arizona (where he remains hugely popular), will be a major battleground in ’08 – Democrats know that no Republican can win without it. McCain’s continuing popularity and credibility in the Hispanic community might also reduce the hemorrhaging of GOP Latino support due to strident anti-immigrant posturing by all major candidates. Moreover, on the abortion issue that inspires and engages so many Republicans, McCain’s unwavering pro-life record would help to solidify the candidacy of either Romney or Rudy if they selected him for the ticket.

Of course, there’s always a chance that McCain (recently surging to second place in New Hampshire) will re-energize his own race for the big prize, or else reject the idea of taking the second spot with one of his rivals.

The very attributes that make him such an attractive candidate for Vice President unfortunately hinder his Presidential campaign – particularly his age, his Senatorial insider status, and the old-hat quality (“You mean he’s running again?”) of his candidacy.

Nevertheless, he still shines at most of the televised debates and he’s conducted the most positive campaign of any of the major contenders, with none of bickering and back-biting so typical of Romney, Rudy, Thompson and, increasingly, Huckabee. In the likely event that McCain’s efforts fall short in pursuit of the Presidential nomination, his selection as a candidate for Vice President would add an element of class and continuity to the Republican ticket.