It's that time again: As the presidential primaries draw to a close, the airwaves are filled with chatter about running mates. The veepstakes inevitably drives the media to circulate a host of irresistible tidbits – marred only by the regrettable fact that they have almost no basis in reality:

1. A vice presidential candidate should win his or her home state for the party.

Long ago, when state parties had tightly run political machines, that logic made some sense, and even into the postwar era it governed many candidates' thinking. But not so much today. More often, the No. 2 either fails to carry his or her home state or simply isn't chosen with such hopes in mind in the first place. Of this year's Democratic contenders, only Ohio Gov. Ted Strickland promises to nab a battleground state for Sen. Barack Obama. On the Republican side, not even Tim Pawlenty, Minnesota's moderate but little-known governor, seems likely to shore up that swing state for the GOP.

2. Ideological and regional balance are vital to a ticket.

This once-powerful logic has eroded as the parties have become more ideologically uniform. Voters today choose their candidates on the basis of image more than party. And although balancing efforts still sometimes occur, nominees will more often use their moments in the spotlight to send signals about their own candidacies. So any ticket-balancing is in the form of signaling neglected constituent groups that they're not taken for granted. This year, Mr. Obama lacks strong support from enough key Democratic voting blocs – Hispanics, Jews, women, gays, seniors and the white working class – that he should be sensitive to their concerns in choosing a veep. John McCain, on the other hand, would do well to bolster his own reputation as a maverick by choosing someone like Colin Powell or Mike Huckabee.

3. Reaching across the aisle to form a bipartisan ticket would be smart politics.

Well, maybe, but it's not going to happen. As weak as parties have become, the choice of a president and a vice president still defines them. To turn to the rival institution in this basic act of self-definition would be an abdication – a concession that the party is nothing but a vehicle for the ambitions of individual politicians, not a coherent body with a purpose.

4. Candidates should think "outside the box."

For candidates, as for housecats, the box is there for a reason.

Those who aren't fantasizing about a bipartisan ticket often dream that a nominee will look outside politics altogether for his or her deputy. (Former Hewlett-Packard chief Carly Fiorina is one name bandied about this year.) Washington loves no cliché more than the cliché of Washington's bankruptcy – the myth that only someone with no political experience, usually a mogul or a financier, can fix our political mess. But most politicians canny enough to get a presidential nomination know that the fall campaign isn't the place for a novice to be learning the game.

5. All of this is beside the point: The choice of a running mate doesn't matter.

Does anyone vote based on the veep? The kibitzing over a nominee's choices is clearly out of proportion to the importance of the selection. But some political scientists do surmise that the choice can shift the popular vote by a smidgen – and even 1 or 2 percent can be enough, in the kinds of close presidential elections we've had in 2000 and 2004, to make all the difference.

David Greenberg is a professor of history and media studies at Rutgers University, a columnist for Slate and the author of "Nixon's Shadow: The History of an Image." He was the winner of the 2008 Hiett Prize awarded in April by the Dallas Institute for Humanities and Culture.