Hillary Clinton and Sen. Timothy M. Kaine  during a campaign rally in Annandale, Va., on July 14. (Carlos Barria/Reuters)

We finally know who the major-party vice-presidential nominees are –  Sen. Timothy M. Kaine of Virginia and Gov. Mike Pence of Indiana.  Not surprisingly, much “veepstakes” speculation leading up to these announcements centered on the usual factors considered to be electorally advantageous: geography and demography.

But much of what you’ve been told about the importance of those usual factors is wrong. Based upon the available empirical evidence, it’s not at all clear that these candidate characteristics will have a significant effect on voters.

It’s true that voters may like a running mate more because he or she comes from the same state or belongs to the same demographic group as those voters. But rarely does this affect their votes. Except in extraordinary circumstances — such as when a running mate is extremely unpopular — people vote based on the presidential candidate, not the running mate.

VP candidates don’t deliver more votes from their home states

Vice-presidential candidates are significantly more popular among home-state voters. But this does not translate into votes.

In our new book, “The VP Advantage: How Running Mates Influence Home State Voting in Presidential Elections,” we analyze what is commonly called the “vice-presidential home-state advantage” — that is, the extent to which running mates improve their tickets’ performance in their home states.  Short answer: There is no vice-presidential home-state advantage, on average.  For example, our analysis of American National Election Study data and internal campaign polls from 1960 cast doubt on whether Lyndon Johnson delivered Texas and other Southern states for John F. Kennedy – the most famous example of the purported home-state advantage.

Now, occasionally, running mates can deliver a home-state advantage. But that effect is conditional: it only happens when he or she comes from a less-populous state and has served that state for many years as an elected official. Think Joe Biden or Edmund Muskie.

The problem, of course, is that less populous states have very few electoral votes, thus making them unlikely to flip the outcome in the electoral college. In Pence’s case, a decisive home-state advantage is particularly unlikely because Indiana was already poised to be a reliably Republican state in 2016. Moreover, while Pence has extensive experience in elected office in Indiana, his home state is too populous to yield a home-state advantage.

But what about his Democratic counterpart, Kaine? He comes from a swing state, and he certainly has the requisite experience to deliver a home-state advantage; he served as the mayor of Richmond, lieutenant governor, governor, and now represents Virginia in the U.S. Senate.

But is that enough? Is Kaine so beloved by voters in his home state that tens of thousands of Virginians will prioritize their affection for a vice-presidential candidate over their policy preferences and their attitudes toward the presidential candidates, to vote as they otherwise would not?  Based on the data, it’s highly unlikely. Virginia is simply too large and diverse of a state for a vice-presidential candidate to sway a statistically significant number of voters who might change the outcome of the election.

This contrasts with the home-state impact of the presidential candidates themselves. Depending on the method and time frame of analysis, as well as the candidate’s party, the home-state advantage for presidential candidates is between roughly 3 and 7 percent.  Even so, don’t expect a presidential home-state advantage to matter this year. After all, New York is one of the most reliably Democratic states in the country, and both Clinton and Trump call the Empire State home.

So what about choosing a VP nominee from an oft-slighted demographic group?

Despite speculation about Hillary Clinton selecting Housing and Urban Development Secretary Julián Castro or Labor Secretary Tom Perez as her running mate, to the disappointment of some, we will have to wait at least four more years to see if a Latino candidate appears on a major political party’s presidential ticket. Clinton did, however, select a Catholic running mate in Tim Kaine.  Will this deliver votes?

To understand how vice-presidential demographic characteristics influence voters, we analyzed the performance of other breakthrough candidates: female (Geraldine Ferraro, 1984; Sarah Palin, 2008); Catholic (Sargent Shriver, 1972; Ferraro, 1984; Joe Biden, 2008, 2012; Paul Ryan, 2012); and Jewish (Joe Lieberman, 2000) running mates. Did those candidates attract greater support from voters within their underrepresented demographic group, in comparison with previous elections?

No. In fact, we find the same pattern of results as for home-state nominees. In each case, female and religious minority voters rate running mates from their own group significantly higher on feeling thermometers. That’s true for women evaluating Ferraro and Palin; for Catholics rating Shriver, Ferraro, Biden and Ryan; and for Jews rating Lieberman.

But again, more positive feelings toward the running mate do not necessarily translate into more votes. After accounting for other factors, gender was not a statistically significant predictor of vote choice in 1984 or 2008. Nor was Catholic identification in 1972, 1984, 2008 or 2012. The one exception was in 2000, when Jewish voters were significantly more likely to vote for the Gore/Lieberman ticket. But Jewish voters were more likely to vote for the Democratic candidate in every presidential election since 1960, and they didn’t feel more warmly toward Lieberman than toward the average Democratic running mate. So it’s not clear that Lieberman’s candidacy actually won more Jewish votes.

By contrast, presidential candidates typically do win a higher percentage of the vote from fellow members of a demographic minority group. Catholics were significantly more likely to vote for Kennedy in 1960, and African Americans were more likely to vote for Barack Obama. John F. Kerry was the exception; Catholics were no more likely than non-Catholics to positively evaluate or vote for Kerry in 2004. Catholic identification with Kerry may have been undercut by some church leaders’ denunciation of his views on abortion during the campaign.

But the overall pattern seems clear: Shared demographic identity does increase voting for presidential candidates, but not for their running mates — the same pattern that we find when examining geographic identity.

In short, voters like vice-presidential candidates who come from the same home state or demographic group, but it doesn’t change their votes for president. By contrast, they are indeed more likely to vote for a presidential candidate who comes from the same region or demographic group.

The available evidence points to an obvious conclusion that’s often lost when discussing running mates. Presidential elections are, first and foremost, about electing a president — not a vice president.

Christopher J. Devine is assistant professor of political science at the University of Dayton.  You can find him on Twitter @ProfDevine. Kyle C. Kopko is assistant dean for academic achievement and engagement, and associate professor of political science at Elizabethtown College. You can find him on Twitter @KyleKopko. They are the authors of “The VP Advantage: How Running Mates Influence Home State Voting in Presidential Elections” (Manchester University Press).

This is an updated version of a post that originally ran on April 25, 2016.