A recent Pew poll showed a sharp change in Americans' political party identification: Democrats now outnumber Republicans 50 percent to 35 percent, as opposed to 2002, when both had 43 percent. These numbers may overstate the Democratic advantage. They measure all adults rather than just voters, and Pew's numbers in 2004 and 2006 were more Democratic than the exit polls. Still, the trend is clear.
What does it mean for 2008? Let me offer three scenarios and reasons why each may not happen.
The Blair scenario. In the early 1990s, Britain's Conservatives were regarded as nasty but competent. Then, Britain was forced to devalue its currency. Mortgage payments shot up, and the Conservatives' reputation for competence vanished. The result: Tony Blair's Labor Party won huge victories in 1997, 2001 and 2005.
The scenario here would be for Democrats to enlarge their congressional majorities and sweep to a 40-state presidential victory in 2008. The Republicans' reputation for competence was damaged by Iraq and Katrina. Under the Blair scenario, they would go further downhill, especially if Iraq is still seen as a losing cause.
Why it won't happen: Labor won only after Tony Blair rebranded the party as New Labor, with moderate policies. If the Old Labor Party leader John Smith had not died suddenly in 1994, to be replaced by the 41-year-old Blair, Labor might have lost or won only narrowly -- or so the British political experts I trust believe.
Here, Democrats don't seem to be rebranding themselves as "new Democrats," as Bill Clinton did successfully in 1992. As for competence, Republicans will have a new leader in 2008, and the candidates now polling the highest -- Rudy Giuliani, John McCain and Mitt Romney -- can plausibly claim that quality.
The Ike scenario. In 1952, the United States was mired in a deadly conflict -- 10 times as bloody as Iraq -- that the incumbent president could not end. Then there emerged a candidate with a record of making life-and-death decisions in war: Dwight Eisenhower. Ike captured the Republican nomination from "Mr. Republican," Robert Taft, and then beat a refreshing new face from Illinois, Adlai Stevenson, who had little military experience. The victory came despite the Democrats' big edge in party identification.
None of the Republican candidates can claim experience just like Ike's. But Rudy Giuliani did command a uniformed force of 40,000 -- which reduced crime in New York City by 64 percent in eight years. John McCain served in combat and has had a record of close attention to military affairs ever since.
None of the leading Democrats have anything comparable. Hillary Rodham Clinton has been a conscientious member of the Senate Armed Services Committee for five years. Barack Obama is, like Stevenson, a fresh face from Illinois. John Edwards was a senator for six years and has been running for president for five. Polls show these three candidates trailing Giuliani and, sometimes, McCain.
Scenario: Giuliani or McCain could win even as voters choose a Democratic or (as in 1952) a very narrowly Republican Congress.
Why it won't happen: Giuliani and McCain are not Eisenhower. And they will be identified with George W. Bush's war policy, whereas Ike was not tied to Harry Truman's.
The Perot scenario. In February 1992, a short billionaire from Texas told CNN's Larry King that he might run for president. Ross Perot was able to partly self-finance a campaign, and his calls for reform stirred voters who were tired of stale, bitter partisan division.
The short billionaire in a position to do something similar in 2008 is New York Mayor Michael Bloomberg. He has high job ratings and stands above partisan politics. With an income said to be $500 million a year, he can completely self-finance a campaign. He is also said to be interested in running. In 1992, many voters were unmoored from old partisan allegiances -- as many seem to be today.
Why it won't happen: A Bloomberg candidacy will probably be viable only if the major parties nominate candidates who reflect their narrow party bases, and they may not. Bloomberg also doesn't have the military experience that made Perot a plausible commander in chief.
Which of these scenarios will happen? I have no idea. All could, and so could others in between. I think we're in a period of open-field politics, like that of 1990-96, which gave us the Blair and Perot scenarios and could have given us the Ike scenario if Colin Powell had run in 1996.