Although the next presidential election won't take place until November 2008, and the nominating conventions won't convene until next August and September, the media have been covering the candidates all through 2007 as though they were running a horse race. What is it about presidential politics that evokes horse-race metaphors?

The media have designated and re-designated the Republican "front-runner": John McCain, then Mitt Romney, then Rudy Giuliani, then Mike Huckabee. The media are also speculating whether Hillary Clinton will lose her front-runner status to Barack Obama.

Next summer, the presidential nominee of each party will take the reins of his party, and hopefully then of government. He - or she - will choose a "running mate," and the losers will become footnotes in history books as "also-rans."

The most fascinating horse-race metaphor that might emerge in this campaign is the "dark horse," a well-recognized label for a long-shot candidate who was not in what is now called the top tier. A dark horse's chance of winning the nomination depends on a deadlock among the leading candidates who are unable to cross the finish line with a majority of delegates.

Early in 2007, the media were confidently announcing that the presidential nominations of both parties would be locked up in the early primaries. It now appears just as likely that the early primaries will confirm the fact that Republicans are divided.

Each of the five top-tier Republican candidates has received endorsements from important Republicans, some of whom have state Republican organizations to deliver delegates, and some with large grass-roots constituencies. No poll shows any of these candidates with anywhere near a majority of Republican support.

A recent New York Times/CBS News poll reported that none of the Republican candidates is viewed favorably by even half the Republican electorate. There is no clear leader: Giuliani was the choice of 22 percent of respondents, Huckabee of 21 percent, Romney of 16 percent, and McCain and Thompson each had 7 percent. Among Republican respondents, 76 percent say they could still change their minds about whom to support. Maybe that's because all five leading candidates are globalists and none of them has a solution for the problem of millions of Americans who have lost jobs or had their wages depressed because of unfair trade agreements, outsourcing of jobs overseas, and insourcing foreign workers. A book of political history from 2003 called "Dark Horse: The Surprise Election and Political Murder of President James A. Garfield" (Carroll & Graf, $16) might provide the model. Kenneth D. Ackerman tells the fascinating story of how the 1880 Republican National Convention in Chicago deadlocked, with three sets of delegates unwilling to abandon their first choice, and a totally unexpected non-candidate dark horse named James A. Garfield was nominated on the 36th ballot and then elected president.

Sen. James G. Blaine of Maine was the first major name placed in nomination, soon followed by New York powerhouse Sen. Roscoe Conkling's nomination of war hero Gen. U.S. Grant for a third term. The third major contender was Treasury Secretary John Sherman, nominated by his friend and campaign manager Sen.-elect James A. Garfield.

The first ballot on Monday, June 7, produced Grant, 304; Blaine, 284; Sherman, 93; and a handful of votes for minor candidates. All were well short of the 379 votes needed to win.

Over the next four hours, delegates cast 18 ballots, every one with a full roll call of states. They broke for dinner and then came back to cast 10 more ballots, despite the heat, the tedium and the hard benches on which they sat. All three blocs seemed equally determined to stand by their man. After those 28 ballots, Grant's total of 304 votes had grown to 307, Blaine's 284 had shrunk to 279, and Sherman's 93 to 91.

When the convention resumed on Tuesday morning to cast the 29th ballot, Sherman's total jumped to 116, but that boomlet faded on the next ballot.

The break came on the 34th ballot, late in the alphabetic roll call of states, when Wisconsin suddenly announced "Sixteen votes for James A. Garfield." Sitting in the Ohio delegation, Garfield jumped to his feet and tried to make a point of order that he had not consented to have his name placed in nomination, but the convention chairman gaveled him down and refused to let him speak. The 34th ballot totaled 312 for Grant, 275 for Blaine, 107 for Sherman, and 17 for Garfield. On the 35th ballot, Indiana and Maryland switched to Garfield, giving him a new total of 50 votes.

The roll call for the 36th ballot became high drama. State after state switched to Garfield. Then Maine announced that all its votes had moved from Blaine to Garfield.

When the balloting reached Ohio, Sherman ceded his support to Garfield, who then won the Republican nomination with 395 votes.

Could Republicans be so divided going into the 2008 Convention that a dark horse could win the nomination?