Who should John Kerry choose as his running mate? That’s the political question of the day. Kerry is keeping mum, but everyone else has weighed in – including Ralph Nader, of all people. Nader recently urged Kerry to nominate Sen. John Edwards of North Carolina.

We can learn much about this coming race by examining Kerry’s options. Let’s start with two dramatic but unlikely possibilities: John McCain and Hillary Clinton. Neither of these beloved but controversial figures has a chance. We can rapidly dismiss Sen. Clinton. Two liberal Northeasterners would make a dream ticket – for Republicans to run against.

The McCain idea is more serious. Kerry himself would love to run with the widely popular senator from Arizona. But it’s not going to happen. His choice could split the Democratic Party. McCain, after all, has been a lifelong Republican and a pro-life conservative. Progressive Democrats would deplore this radical move toward the center and might easily defect – to Nader or to the sidelines.

Republicans would be even more outraged by a McCain nomination. They would round on the “traitor” with vicious hostility. Over three months, their verbal onslaughts could badly tarnish his positive image. Republicans would also use this decision to rev up their current strategy of calling Kerry unreliable, a “flipflopper” with no principles.

McCain himself has often said that he has no intention of running as vice-president – with either Kerry or George W. Bush (whose people have cunningly sent up trial balloons for this idea). Let’s take McCain at his word. Kerry could still benefit from his popularity. Hint strongly that he’d offer the senator a major cabinet post – say, Defense. That would give Kerry the best of all worlds. He ends up recruiting McCain (in effect) without forcing him to run in the spotlight for three months as a “defector.”

What are the more serious possibilities? Kerry must find someone who can help him win in the twelve to fifteen truly competitive states. Consider Florida, the state that couldn’t vote straight in 2000. If Kerry by himself could take all the states won by Al Gore four years ago, then a little help in taking Florida would give him an Electoral College majority. Wouldn’t it be logical to nominate a popular Florida leader as VP? He is considering either Bob Graham or Ben Nelson, Florida’s two senators.

This strategy, however, puts too many eggs in one basket. Neither Graham nor Nelson has shown any vote-getting ability outside their state, so they’d add nothing to Kerry’s quest if they couldn’t help him take Florida. But could either deliver the goods? Their clout pales in comparison to Florida Gov. Jeb Bush, who’s not only powerful but popular statewide. In a pinch, would you bet against the governor pulling things out once again for big brother?

Another option calls for Kerry to focus on the Midwest, where a significant number of states are in play. Several Midwestern Democrats have been suggested: Tom Vilsack, governor of Iowa; Evan Bayh, senator from Indiana; Debbie Stabenow, senator from Michigan; and Richard Gephardt, representative from Missouri.

But of these people are unknown quantities at the national level. You can be popular and self-assured in your home state, but seem callow, anxious, and unpolished when the glare of the national spotlight hits you. Remember Dan Quayle, Spiro Agnew, and most disastrous of all, Tom Eagleton?

Of course, Richard Gephardt must be considered a contender. If he simply carried his home state of Missouri, Democrats could win back the White House. But can he do it? Gephardt hasn’t won much beyond his single congressional district in St. Louis, faring badly in two runs for the presidency.

Another strategy for Kerry is to “go ethnic” and choose Bill Richardson, current governor of New Mexico and Hispanic in origin. Richardson would insure the continued presence of closely-divided New Mexico in the Democratic camp, and his broader ethnic appeal could presumably help win neighboring Arizona and Nevada, shore up Democratic support in California, and possibly even tip the balance in Florida. But Richardson poses a risk: he’s relatively untested nationally and something of a loose cannon.

Some Democratic strategists pin their hopes on retired general Wesley Clark. With this choice Kerry would be suggesting that Democrats can compete with Republicans on military and defense matters. But that strategy might not work. It’s hard to shift voter images of the two parties, and even a Kerry-Clark ticket wouldn’t be enough to win citizens focused mainly on security issues. Besides, Clark’s weak performance in the primaries suggests little ability to bring in the added voters Kerry needs.

That leaves Kerry with one last, and perhaps best, candidate: John Edwards. Nader could be right, after all. The selection of Edwards appears a no-brainer. He’s a tested candidate – no skeletons emerged from his closet in months of campaigning for the presidency, and he proved a popular, well-respected man on the campaign trail. Unlike most other contenders, he’s a national figure who has faced the glare of the spotlight without making fatal mistakes.

In Edwards, Kerry would be balancing his ticket in terms of age and style (if not ideology). Edwards could help him gain those few additional voters in several swing states – Ohio, Pennsylvania, Missouri, Iowa – to tip the balance of the Electoral College toward Democrats.

An Edwards strategy also helps Kerry minimize potential losses. Who would vote against this ticket just because of Edwards? True, some people mumble about his “trial lawyer” background, but they’re mostly conservatives to begin with. This is hardly an issue that resonates widely in the electorate. So Edwards wouldn’t lose Kerry anything – and his sunny optimism and youthful vigor might serve the ticket well.

We currently live in a “50-50 nation.” Polls show the two parties just about even in popular support. They each hold about half of all public offices. In these contested circumstances, any single event can make the crucial difference between victory and defeat. Kerry’s vice-presidential pick is a choice that could determine the outcome of this election – and the shape of American politics for years to come.

Oliver Woshinsky is a political science professor emeritus at the University of Southern Maine.