Who should Trump and Clinton pick as running mates? This research says it doesn’t really matter.

Even with the Democratic and Republican Party presidential nominations yet to be decided, already we are hearing muchspeculation about the 2016 “veepstakes.” Not surprisingly, most of this speculation focuses on the usual factors considered to be electorally advantageous: geography (think home state) and demography (think gender and ethnicity).

But much of what you’ve been told about the importance of those usual factors is wrong.

It’s true that voters may like a running mate more because s/he 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, citizens vote based on the presidential candidate, not the running mate. Vice presidential candidates are significantly more popular among home state voters (measured via 0-100 “feeling thermometers”). Yet this does not translate into votes.

In our newly published book, “The VP Advantage: How Running Mates Influence Home State Voting in Presidential Elections” (Manchester University Press), we use a multi-method approach to analyze what is commonly called the “vice presidential home state advantage” — that is, the extent to which running mates improve their ticket’s performance in their home state. No matter the empirical method — including Michael Lewis-Beck and Tom Rice’s foundational model measuring deviations in home state voting trends, as well as regression models using state-level data and individual-level data from the American National Election Studies — we consistently find that the vice presidential home state advantage is, statistically speaking, zero.

Now, occasionally, running mates can deliver a statistically significant home state advantage. But that effect is conditional: It only happens when s/he comes from a relatively less-populous state and has served that state for many years as an elected official. Think Joe Biden. ...