Few presidential elections in the country's history have offered front-running candidates with such glaring political weaknesses.

On the Republican side, Sen. John McCain's maverick streak infuriates fiscal and social conservatives, the two blocs responsible for past GOP successes. On the Democratic side, Sen. Barack Obama's inexperience on foreign policy feeds perceptions of an empty suit with soaring but hollow rhetoric. Conversely, Sen. Hillary Clinton's shrill partisanship energizes the Republican base more than her own party.

Amid that political landscape, the selection of vice presidential candidates is no mere squabble over symbols. This year's running mates hold the potential to inform and reshape more greatly the campaigns they join. Accordingly, supporters for the respective candidates have begun wringing their hands over short lists.

Governors populate those lists more than in past elections due to sagging approval ratings for Congress. Politicians in critical swing states are also favored choices.

Beyond such general considerations, the two Democrats have a credibility gap to fill on the matter of national security. Left-leaning blogs are abuzz with vice presidential candidates who could match McCain in experience and knowledge and convince independents that either a Clinton or Obama administration would be capable of keeping the country safe.

At the recent National Governors Association meeting in Washington, D.C., late last month, Democrats touted their foreign-policy experience. Gov. Kathleen Sebelius of Kansas, a potential pick for the Obama camp, stressed that governors oversee the National Guard in their respective states and that many have visited Iraq, Afghanistan, and Pakistan.

Speaking with greater candor, Gov. Ed Rendell of Pennsylvania lamented that most governors lack the kind of overseas experience needed on the Democratic ticket.

McCain solves that issue for Republicans but creates about a half dozen more with his departures from GOP orthodoxy. Rep. John Shadegg of Arizona, who has witnessed McCain successfully alleviate concerns of conservatives in his state over the years, believes the vice presidential pick is a critical piece to uniting the party.

But Shadegg told WORLD that McCain's personality and character will ultimately do more for unity than his running mate: "The single most important factor in any election is trust. And the people of Arizona have come to trust John McCain. Just like Barry Goldwater, they came to trust him and then tolerated him on issues where they disagreed."

McCain has sought to transfer that state model to his national campaign and has succeeded in winning support from respected fiscal conservatives like Sen. Tom Coburn of Oklahoma and social conservatives like evangelical leader Gary Bauer. His pick for vice presidential nominee will likely be someone who can add to party unity.

"The fact that people of very different philosophical stripes within our party are willing to step forward and vouch for him is a huge asset," Shadegg said. "Say what you want about John McCain, and I've disagreed with him many times, but the guy demonstrates courage, and that is his single greatest strength."

Veepstakes: Handicapping the race

Democrats

Swing state

Bill Richardson: The New Mexico governor didn't prove much of a presidential campaigner, but the combination of swing state help, Hispanic appeal, and foreign policy experience renders Richardson a strong choice for either Clinton or Obama. He's a symbolic pick that would outshine neither.

Ted Strickland: The Ohio governor has stated publicly that he would not accept the nomination for vice president, but a Clinton comeback could change his mind. Ohio proved a pivotal state in 2004, and Strickland's appeal to independents and even some Republicans could have Clinton knocking at his door.

James Webb: The Virginia senator could put an increasingly purple state in play with his military background and Reagan-Democrat appeal. But Webb's inexperience could hurt the already green Obama ticket. And his curt, confrontational style and high negatives among independents would underscore Clinton's weaknesses.

Mark Warner: The former Virginia governor would need to abandon his race for senator, a high price in a year Democrats dream of pushing near the magic number of 60 Senate seats. But Warner's value on a national ticket could prove worth the cost given his McCain-like draw among independents.

National security

Joe Biden: The Delaware senator routinely outclassed the Democratic frontrunners in foreign policy knowledge during debates last year. Though he made little headway in national polls and suffers from chronic foot-in-mouth disorder, Biden could spare Obama from embarrassment in foreign policy head-to-heads with McCain.

Wesley Clark: The retired four-star general matches McCain wound-for-wound in American hero status and would lend credibility to Democratic positions on Iraq. Clark's lack of polish, which led to several gaffes in his 2004 presidential campaign, cannot outweigh his strong appeal in the South and among the party's netroots.

Evan Bayh: The Indiana senator has won five elections in a very red state, including two for governor. A collegial moderate, Bayh appeals to independents. And the bulk of his work in Congress has centered on foreign policy matters. He would help soften the abrasive image of Clinton, to whom he is fiercely loyal.

Wild cards

Kathleen Sebelius: The Kansas governor is widely considered Obama's first choice as she would offer a female alternative to disappointed Clinton supporters. Sebelius has twice won elections in a conservative state and also maintains strong ties in Ohio, where her father was governor in the 1970s.

Janet Napolitano: The Arizona governor has little chance of bringing McCain's home state into play, but her presence on an Obama ticket might force the GOP candidate to spend more resources in Arizona than he otherwise would. Napolitano is tough on terror and illegal immigration, potentially balancing Obama's more liberal positions.

Clinton/Obama: Given primary turnout, a Clinton-Obama or Obama-Clinton ticket would prove near unbeatable in November. Many in the party will call for it once the nominee is chosen. But the longer a bitter primary battle extends, the less likely the two candidates will be able to reconcile.

Republicans

Swing state

Tim Pawlenty: The Minnesota governor is a longtime McCain supporter and will host the Republican convention in his critical swing state this August. Pawlenty leans right on matters such as taxes, immigration, and the war, but could upset already disgruntled conservatives with his global warming crusading.

Charlie Crist: The Florida governor could become McCain's top choice should polls in the state show Clinton or Obama with a lead. A victory in Florida would far outweigh whatever national negatives Crist carries, such as his support for the right to die and his backing of strict government caps on greenhouse-gas emissions.

Mel Martinez: The Florida senator would rally the Latino vote in a critical state. And his 96 percent lifetime rating with the American Conservative Union could appease the right-wing base. But Martinez is a native of Cuba and thus constitutionally barred from occupying the presidency, a major detraction for the second in line.

Unifying the party

Jim DeMint: The South Carolina senator represents the heart of red-meat conservatism with his support for school choice, free-market health care, and strict fiscal discipline. DeMint's presence on the ticket would prove McCain's commitment to the GOP base but might smack of pandering among independents.

Mitt Romney: The former Massachusetts governor has a massive following within the party and wads of cash. Romney could lead the charge of rallying conservatives behind McCain, but such a ticket seems unlikely given the two candidates' mutual disdain apparent during primary debates.

Condoleezza Rice: The secretary of state would help the GOP play instant catch-up in the hype over social advancement. The election would no longer be about race or gender and could instead center on issues and policy disputes. That benefit might outweigh Rice's connection to an unpopular administration.

John Thune: The South Dakota senator is something of an anti-McCain in his youthful movie-star looks and consistent conservatism. The pair shares a penchant for straight shooting, and Thune, a Biola graduate, would help the ticket among evangelicals and Californians, two contingents McCain will chase hard.

J.C. Watts: The former Oklahoma congressman was once considered a rising star in the GOP until he left political office to spend more time with his family. A journalist and former Baptist minister, Watts is a gifted communicator and may mitigate the Obama advantage among African-Americans.

Bobby Jindal: The Louisiana governor is the next Ronald Reagan, according to Rush Limbaugh. Jindal's Indian-American heritage could neutralize Obama's multicultural advantage. And his presence would signal talk radio's king that the McCain camp is listening. One hang-up: Louisiana may need Jindal more than America does.

Wild cards

Joe Lieberman: The Connecticut senator is an independent who caucuses with Democrats. His selection to the GOP ticket would constitute a finger jab into the eyes of conservatives, but such cross-aisle maverick moves are a McCain trademark. So is winning elections, a goal that should keep Lieberman off the ballot.

Mike Huckabee: The former Arkansas governor moved from a third-tier also-ran to a top-tier contender this primary season, despite miniscule funds. That skill earned McCain's respect. Huckabee's centrist positions on immigration and spending would draw howls from the conservative base.