Republicans and Barack Obama are far apart ideologically, but they have a common enemy: Hillary Clinton. This explains why many Republicans look kindly on Obama's bid for the Democratic presidential nomination. Republicans have two goals in the 2008 race. One is to retain the presidency. The other is to deny the Clintons--Hillary and Bill--another four (or eight) years in the White House.

Thwarting the Clintons won't be easy. Hillary Clinton is nowhere near as close to losing the Democratic nomination as many in the political community believe. It's true she doesn't inspire. In debates, she constantly flashes a fake smile and, when unnerved, unleashes a contrived laugh--aka, the cackle. She attracts far smaller and considerably less enthusiastic crowds than Obama does. And his fundraising now dwarfs hers.

But Clinton has already survived two crushing defeats, first in Iowa, then in South Carolina, only to rise again on Super Tuesday with a string of lopsided victories in blue states the Democratic nominee must carry in November. Obama did better in red states that are less important to Democrats in a general election.

For all her unattractiveness as a candidate, Clinton has put together an impressive, and seemingly durable, coalition of women, seniors, Hispanics, and the less-than-wealthy. In the California primary last week, she lost the white vote to Obama by 49 percent to 43 percent, yet won the state in a near-landslide: 52 percent to 42 percent.

Mark Penn, Clinton's chief strategist, has been ridiculed for his rosy analysis of her campaign. But

That system is all but certain to prevent either candidate from capturing the nomination in the remaining primaries and caucuses. Leaving aside the 796 super-delegates--chiefly elected and party officials--Clinton or Obama would need to win roughly three-fourths of the delegates in these states to wrap up the nomination. With proportional distribution of delegates, that's practically impossible.

So the nomination, in all likelihood, will be left up to the super-delegates. About half of them have already endorsed a candidate. Of these, Clinton leads by 90 delegates--a not insubstantial number. (Obama needs to steal super-delegates who've endorsed her to win.)

Clinton's strategy: a strong finishing kick. The states with primaries and caucuses over the next few weeks favor Obama, which means he'll likely take a narrow lead in delegates.

But there are three big primaries at the end of the process--Ohio and Texas on March 4 and Pennsylvania on April 22. In all three, Clinton starts with an advantage. Governors Ted Strickland of Ohio and Ed Rendell of Pennsylvania are backing Clinton, and their statewide organizations are a significant asset. In Texas, Hispanics are a major part of the Democratic electorate.

If Hillary wins all three states, it's hard to imagine the super-delegates denying her the nomination. And a primary hat trick is not inconceivable. Just winning two of three would probably make her the hotter candidate--assuming she leads Obama in popular votes over the entire campaign.