Q: Historically, have vice presidential candidates really helped win states in the general election?
A: Presidential nominees don't pick their running mates based on this strategy as often as one might think. Even when they do, the results are decidedly mixed.
FULL ANSWER
It's common every four years to hear speculation that a candidate's choice of a certain running mate could put the running mate's home state in his column. This year, for instance, some Democrats had been urging their presumptive presidential nominee, Barack Obama, to pick Sen. Jim Webb of Virginia to fill out the ticket, because Webb might help flip Virginia from a red state to a blue one. (Webb took himself out of the running in early July, however.) Similarly, Obama's Republican counterpart, John McCain, may be thinking of teaming with Minnesota Gov. Tim Pawlenty, news sources say, because his campaign's internal polling shows Pawlenty could help deliver Minnesota, and neighboring Wisconsin.
The last two U.S. presidential elections were squeakers, so it's not surprising that the expected nominees might look to veep selection as a way to get an edge in a battleground state. In recent history, though, candidates' running mates either haven't been chosen for reasons of geography or, if they have, the strategy mostly has flopped.
Let's begin with the last two elections. It's safe to say that Dick Cheney wasn't picked by George Bush for reasons of geography. Cheney actually had been living and voting in Texas, but he moved his voter registration to Wyoming when it became clear that he was a contender for the v.p. slot. The 12th Amendment to the Constitution prohibits electors from voting for two people from their own state, so the Bush-Cheney ticket would have forfeited Texas' 32 electoral votes if Cheney had kept his residency in the Lone Star state. The choice of Wyoming made sense for Cheney – he'd grown up there and represented the state in Congress – but it was no help to Bush. The state had been reliably Republican for decades.
To the extent that John Edwards was chosen by Democratic nominee John Kerry in 2004 for his Southern roots, it didn't help the Dems' electoral count. The two failed to carry Edwards' home state of North Carolina. In 2000, Al Gore likely didn't need Joe Lieberman to win Connecticut, which had voted Democratic in the previous two presidential election cycles and didn't bring many electoral votes in any case. Lieberman was chosen for other reasons – perhaps his perceived moral rectitude, as Gore tried to distance himself from the scandal-tarred Bill Clinton, and the fact that he was the first Jewish major party nominee for either of the nation's top two posts.
The best example of a vice presidential nominee actually being a definitive force in carrying a state, according to at least one self-styled expert on the topic, is probably Sen. Edmund Muskie, who ran with Hubert Humphrey on the Democratic ticket in 1968. Muskie's home state of Maine had voted Republican since 1916, except for the 1964 Democratic landslide, and went Republican again in 1972 and several elections beyond.
That said, when it comes to choosing a No. 2 for a presidential ticket, there are so many factors in play in any given election that it's almost impossible to make a definitive judgment about the relative weight of any of them.
–Viveca Novak
Sources
"U.S. Electoral College: Historical Election Results." U.S. National Archives and Records Administration.
"Can a VP Nominee 'Win' A State?" fivethirtyeight.com, accessed 9 July 2008.
Kornacki, Steve. "Look Who's Back: It's Gore and Lieberman in '08." The New York Observer, 20 June 2008.
Raasch, Chuck. "Edwards brings pluses, risks to Kerry campaign." USA Today, 6 July 2004.
"Webb to Remain in Senate, No Longer VP Candidate." abcnews.com, accessed 9 July 2008.
Pethokoukis, James. "Source: McCain Vice President Search Now Focuses on Pawlenty." U.S. News & World Report, 19 June 2008.
Johnson, Glen. "Early Knack for Leading put Cheney on Fast Track," The Boston Globe. 26 July 2000.