It is possible to muscle your way into a vice presidential nod: You have something the nominee wants, and he has to give it to you.
The question is: Does Hillary Clinton have that kind of muscle?
Her victories in states such as Ohio, Pennsylvania and West Virginia and her strength with women and white working-class voters have fueled the argument that Barack Obama must put her on the ticket if he wins the nomination and wants those states and those votes in the fall.
And, as a senior Obama adviser told me Wednesday, some Clinton supporters are "pushing real, real hard to get her on the ticket."
But it won't be easy.
"You don't want your vice president taking away anything from the ticket, and she does," said the adviser, who asked not to be named because he was expressing his personal views and not the official view of the campaign.
The adviser cited two things against Clinton: the number of voters who consider Clinton "dishonest" and the "baggage" Clinton brings with her.
Last month, a Washington Post-ABC News poll found that nearly six in 10 Americans believe Clinton is not "honest and trustworthy."
"That's not a real positive," the Obama adviser said, adding: "Her baggage in a general election is real. Does she bring women? No question. But Barack Obama is not a turnoff for women."
He added: "Keep in mind, we are talking about Democratic women. That's who have been voting for her in the primaries. Do you really think Democratic women are going to vote for John McCain in a general election with the Supreme Court at stake?"
But doesn't Clinton also attract certain groups of white voters that Obama has been unable to get? "Yes," the adviser said, "but some of them will never vote for Obama anyway."
Bruce Morrison disagrees with all of this. He is a former congressman from Connecticut, went to Yale Law School with Hillary and Bill Clinton, was co-chairman of Irish-Americans for Clinton-Gore and has worked closely with Hillary Clinton on immigration issues.
He told me that if Obama wins the nomination, putting Clinton on the ticket just makes sense. In fact, when Clinton was doing well earlier in the year, he urged her to put Obama on the ticket.
"This is a race which is as close to a tie as anything we can recall," Morrison said. "The party is divided along certain sorts of measurable lines. Different kinds of people are on different sides, and what the party needs is a merger."
But what about Clinton's "baggage"?
"Whatever baggage she has, it is obvious that people are supporting her in large numbers," Morrison said. "Her baggage is that she has taken slings and arrows for 20 years and is still standing."
Morrison added: "When she says she is winning battleground states in primaries, that argument is relevant. Putting her on the ticket makes it more likely for the ticket to win Pennsylvania, Ohio, Michigan and West Virginia in the general election."
The selection of a vice president is more than a cold calculation, however. Part of the decision is about comfort level. It is about the nominee asking: "Do I want this person hanging around me for the next four or eight years?"
And, in the case of Hillary Clinton, it is also about asking: "Do I want Bill Clinton hanging around me for the next four or eight years?"
Which is a question I put to Morrison.
"I think Bill is a resource," Morrison said. "He can be unhelpful. He has been, at times, unhelpful in this campaign. But on the whole, he has been an enormous resource."
Morrison says putting Hillary Clinton on the ticket would have impact with voters. She would, he says, bring "white, working-class" people to the ticket, "the white ethnic voters" with whom Bill Clinton did well in 1992 and 1996 and with whom Al Gore and John Kerry did not do so well in 2000 and 2004.
Morrison does not diminish Obama's accomplishments. "We have two really spectacular candidates," he said. "They have stood up pretty well in a grueling battle for two years, and both are still standing. Neither has knocked the other out, and one is winning in the stretch."
But Morrison said the choice of a vice president would be seen as Obama's "first presidential decision," and picking Hillary Clinton would reflect "the idea of bringing people together, the centerpiece of his campaign." It would be, in other words, a good symbol.
In the end, though, it will still be about muscle.
"A lot of Democrats are very strongly for Hillary and much less so for him," Morrison said. "The most efficient, most dramatic and most effective way to get them is to pick her."