New Hampshire was recently brightened by the presence of Barack Obama, 45, who, calling the fuss about him "baffling," made his first trip in 45 years to that state, and not under duress. Because he is young, is just two years distant from a brief career as a state legislator and has negligible national security experience, an Obama presidential candidacy could have a porcelain brittleness. But if he wants to be president -- it will not be a moral failing if he decides that he does not, at least not now -- this is the time for him to reach for the brass ring. There are four reasons why.

First, one can only be an intriguing novelty once. If he waits to run, the last half-century suggests that the wait could be for eight years (see reason four, below). In 2016, he will be only 55, but there will be many fresher faces.

Second, if you get the girl up on her tiptoes, you should kiss her. The electorate is on its tiptoes because Obama has collaborated with the creation of a tsunami of excitement about him. He is nearing the point when a decision against running would brand him as a tease who ungallantly toyed with the electorate's affections.

Third, he has, in Hillary Clinton, the optimal opponent. The contrast is stark: He is soothing; she is not. Many Democrats who are desperate to win are queasy about depending on her. For a nation with jangled nerves, and repelled by political snarling, he offers a tone of sweet reasonableness.

What people see in him reveals more about them than about him. Some of his public utterances have the spunginess of Polonius' bromides for Laertes ("neither a borrower nor a lender be ... to thine own self be true"). In 2005, the liberal Americans for Democratic Action and the AFL-CIO rated his voting record a perfect 100. The nonpartisan National Journal gave him a 82.5 liberalism rating, making him more liberal than Clinton (79.8). He dutifully decries "ideological" politics, but just as dutifully conforms to most of liberalism's catechism, from ``universal'' health care, whatever that might mean, to combating global warming, whatever that might involve, and including the sacred injunction Thou Shalt Execrate Wal-Mart -- an obligatory genuflection to organized labor.

The nation, which so far is oblivious to his orthodoxy, might not mind it if it is dispensed by someone with Obama's "Can't we all just get along?" manner. Ronald Reagan, after all, demonstrated the importance of congeniality to the selling of conservatism.

Fourth, the odds favor the Democratic nominee in 2008 because for 50 years it has been rare for a presidential nominee to extend his party's hold on the presidency beyond eight years. Nixon in 1960 came agonizingly close to doing so (he lost the popular vote by 118,574 -- less than a vote per precinct -- and a switch of 4,430 votes in Illinois and 24,129 in Texas would have elected him), but failed. As did Hubert Humphrey in 1968 (he lost by 510,314 out of 73,211,875 votes cast), Gerald Ford in 1976 (if 5,559 votes had switched in Ohio and 7,232 votes had switched in Mississippi, he would have won) and Al Gore in 2000 (537 Florida votes). Only the first President Bush, in 1988, succeeded, perhaps because the country desired a third term for the incumbent, which will not be the case in 2008. So the odds favor a Democrat winning in 2008 and, if he or she is re-elected, the Democrat nominated in 2016 losing.

Furthermore, remember the metrics of success that just two years ago caused conservatives to think the future was unfolding in their favor: Bush carried 97 of the 100 most rapidly growing counties; the center of the nation's population, now southwest of St. Louis, is moving south and west at a rate of two feet an hour; only two Democratic presidents have been elected in the last 38 years; in the 15 elections since World War II, only twice has a Democrat received 50 percent of the vote. Two years later, these facts do not seem so impressive.

In 2000 and 2004, Bush twice carried 29 states that now have 274 electoral votes; Gore and Kerry carried 18 that now have 248. Not much needs to change in politics in order for a lot to change in governance. And Obama, like the rest of us, has been warned, by William Butler Yeats: All life is a preparation for something that probably will never happen.

Unless you make it happen.