OK, so Sen. Hillary Rodham Clinton (D-N.Y.) is staying in the presidential race despite losing among elected delegates, facing a slimming lead among superdelegates, losing the popular vote and behind by 2-to-1 in the number of states carried. She slogs on, hoping against hope for a sudden turnaround in the race.

Apart from the psychological reasons for her stubbornness, is there a more subtle political calculation going on?

Is she continuing her race so as to have a platform from which to continue to bash Sen. Barack Obama (D-Ill.) in the hopes of so damaging him that he can’t win the general election? Is she doing this to keep her options alive for the 2012 presidential race?

Hillary is obviously entitled to keep running until Obama has secured the votes necessary for the nomination, and it is certainly understandable that she would want to run until the last popular vote is counted. But must she run a negative, slash-and-burn campaign? Must she use her time on the platform and on television to belittle, mock, deride and try to destroy the man who will eventually be the candidate of her own party?

Former Arkansas Gov. Mike Huckabee (R) felt similarly justified in staying in the race for the Republican nomination until Sen. John McCain (R-Ariz.) reached the majority threshold required for nomination. He contested the Texas primary vigorously, even though his earlier losses in South Carolina and Florida made it most unlikely that he could win the nomination. But he chose to run a positive campaign. He didn’t knock McCain. He just articulated the case for his own candidacy.

But Hillary won’t avail herself of that option because it does not serve her long-term fallback position: a shot at the nomination in 2012. If Obama is elected this year, he will seek reelection in 2012 and Hillary would have to face taking on an incumbent in a primary in her own party if she wanted to run, a daunting task. But if McCain wins, the nomination in 2012 will be open. And it might be worth having. McCain will be 76 years old and the Republican Party will have been in power for 12 years. Not since FDR and Truman has a party lasted that long in power. When the Republicans tried to do so, in 1992, they fell flat on their face.

Hillary is using white, blue-collar fears of Barack Obama to try to stop him from getting nominated or elected.

She is playing on his “elitism” by hammering him on blue-collar issues and is mincing no words in painting him as a stranger to blue-collar white America.

Hillary is attracting the votes of cops, firefighters, construction workers, union members. Are they in love with Hillary? They can’t stand her. But they are terrified of the Rev. Jeremiah Wright, William Ayers and the various influences to which Obama seems to be subject. By playing on those fears, Hillary is undermining Obama’s ability to get elected.

This is not a byproduct of her continued candidacy — it is the goal. She, the consummate realist, must know that she has no practical shot at the nomination herself after her numbing loss in North Carolina and her paper-thin margin in Indiana. But she welcomes the opportunity an ongoing candidacy offers to bash Obama and to drive a wedge between him and the voters he must have to beat McCain.

The question is how long Democratic primary voters and the party leadership let her go on hitting their ultimate nominee. Will they bring Hillary up short and speak out about the harm she is doing to their party’s prospects by way of her refusal to recognize reality?

Hillary doesn’t have to pull out. She is entitled to run in the remaining states. But she should curtail her negative campaign and adopt the Huckabee strategy: Maximize your own vote share, but don’t beat up the party’s nominee. Unless, of course, that is her goal all along.