Whose ‘dream ticket’?

The idea won’t die. As Barack Obama has all but sewn up the Democratic nomination, pundits continue to float the idea of a dream ticket, this time with Hillary Clinton as the vice presidential choice. Its proponents say the “Dream Ticket” would draw in Mrs. Clinton’s supporters, ward off any possible embarrassing problems at the convention, and result in the party’s easy victory in November.

The dream ticket is actually a good name for this arrangement. Unfortunately for the Democrats, it happens to be John McCain’s dream. For the Democrats in 2008, the selection of Mrs. Clinton as the vice presidential pick could prove disastrous.

This may be a bit of a surprise. After all, the vice presidential choice generally does not have much of an impact on a presidential race. Studies have found voters do not cast their ballots based on running mates. While there are a couple of examples of vice presidents who seemed to help provide a momentum boost to the ticket, such as Senator Ed Muskie in 1968 and Al Gore in 1992, the only running mate choice who may have played a major role in the election was Lyndon Johnson in 1960.

In the same vein, Richard Nixon, one of only two men to be involved in five national races as a presidential or vice presidential candidate, believed a vice presidential choice could only harm the ticket.

Even the very bad selections may not have made much of a difference. Dan Quayle did not damage George H.W. Bush’s successful run in 1988, nor was George McGovern’s aborted selection of Sen. Thomas Eagleton responsible for his overwhelming defeat.

But Hillary Clinton might be different. The reasons for choosing Mrs. Clinton are obvious. She ran a close second in the primaries and she appears to have a hard-core group of supporters who threaten to bolt the party or not vote at all if she does not get the nomination. Giving her a running mate slot would almost certainly mollify the voters threatening to vote against Mr. Obama.

But there are critical reasons for Mr. Obama to look elsewhere. Some of the negatives are ingrained in the system, which is why few runner-ups are ever chosen as a running mate. Since Kennedy chose Johnson in 1960, there have been only two other runner-ups selected to run as VPs, John Edwards in 2004 and George H.W. Bush in 1980. And George H.W. Bush was selected only after Reagan had a high-profile flirtation with former President Gerald Ford.

The problem is that choosing a runner-up invariably means trying to sweep under the rug the many criticisms and negative statements made during the primary campaign. So, while the two candidates can easily get over any bad feelings from the primary, they will have a much harder time convincing voters that Mrs. Clinton all of a sudden believes Mr. Obama has enough experience to serve as president.

But there is an even more important reason to avoid Mrs. Clinton. With her as his running mate, Mr. Obama would tie himself to one of the most polarizing figures in American politics. The dislike she engenders could actually drive up both Republican turnout and fund-raising.

It also is hard to believe many Clinton supporters will either stay home or vote for Mr. McCain or some third party candidate. As happens after nearly every hard-fought presidential primary, nearly all the voters gravitate back to their party’s standard bearer by November. The disgruntled voters quickly discover that however much they preferred the losing candidate in the primary, the opponent’s positions are much closer to their own then any of the other presidential options.

For example, Clinton supporters may be upset now, but after months of commercials barraging them with McCain positions, on abortion or foreign policy, they probably will pull the lever for Mr. Obama.

The benefit of selecting Mrs. Clinton probably represents at most a tiny fraction of her supporters. But the cost of exciting the Republican base could mean she, more than any other vice presidential candidate in recent history, could cost the ticket votes and even critical states.

The Dream Ticket has a nice ring to it. It seems like an obvious, fair choice — two candidates did well in the primaries so they both should get on the ballot. Unfortunately, because of natural weakness in the candidate and in the primary system, it could end up being the Democrats’ nightmare instead.

Joshua Spivak, a public relations executive and attorney, is a research fellow at the Hugh L. Carey Center for Government Reform at New York’s Wagner College.