Vance, Donalds and Carson have credibility issues. Trump should be wary.

Christopher J. Devine is an associate professor of political science at the University of Dayton. He is the author of "Do Running Mates Matter? The Influence of Vice Presidential Candidates in Presidential Elections” (with Kyle C. Kopko) and “I’m Here to Ask for Your Vote: How Presidential Campaign Visits Influence Voters.”

Donald Trump has reportedly narrowed his list of potential vice-presidential running mates.

Conventional wisdom is his VP should be someone who helps win the election by delivering a home state or a key voting bloc. No finalists come from a top battleground state.

Perhaps U.S. Rep. Elise Stefanik could help Trump with women; U.S. Sen. Marco Rubio with Latinos; or U.S. Sen. Tim Scott, U.S. Rep. Byron Donalds or former Housing and Urban Development Secretary Ben Carson with Black voters.

The conventional wisdom is wrong.

People vote for presidential candidates, not a vice president.

Who Trump chooses doesn't really matter

My book with Kyle C. Kopko, "Do Running Mates Matter?," shows vice-presidential candidate evaluations have very small, direct effects on presidential voting. Running mates rarely have targeted effects on voters from their home state or demographic group.

All about the VP picks: Trump's VP options: Sizing up their pros and cons from Ohio's JD Vance to Vivek Ramaswamy

Geraldine Ferraro in 1984 and Sarah Palin in 2008, had no discernible effect on votes among women. Evangelicals didn't swing toward Trump after he chose Mike Pence in 2016. Kamala Harris did help Joe Biden win Black and women voters in 2020, but not by much.

It is very unlikely Trump’s running mate will decide this election.

Here’s a better strategy: Choose a well-qualified running mate, who is ready to serve as vice president — or president, if necessary.

Voters reward presidential candidates for choosing a credible running mate and punish them for not doing so. For example, in 2008, Barack Obama’s selection of Joe Biden boosted evaluations of his judgment and won him additional votes. John McCain’s selection of Palin had the opposite effect.

Trump’s choice likewise will shape voters’ expectations about his second term in office.

The issue with Vance, Donalds and Carson

Is he serious about governing, or focused on retribution against his opponents? Will he be more successful working with Congress to enact his policy agenda? Will he demand absolute loyalty from his subordinates?

Some of Trump’s finalists would not be particularly credible. U.S. Sen. J.D. Vance is a first-term senator. Donalds is a second-term congressman. Carson has never held elective office and served only one term as a cabinet secretary.

Voters are unlikely to view them as well-qualified to be President Trump’s right-hand man or to potentially take over as commander-in-chief.

The remaining finalists would lend Trump more credibility.

Stefanik is a five-term congresswoman and chair of the House Republican conference. Scott is serving his third term in the Senate. U.S. Sen. Tom Cotton has served in the House and Senate for more than a decade. Doug Burgum has no federal government experience but has been North Dakota's governor for eight years following a successful career in business.

Rubio's the best man for the job

Trump's best choice is Marco Rubio.

He has 25 years of experience in local, state and federal office, and is in his third term as a U.S. senator from Florida. (Rubio would have to switch residence to a different state to run with Trump, a fellow Floridian.) He has served as speaker of the Florida House of Representatives and chaired the Senate's intelligence committee.

As a former Trump rival for the Republican presidential nomination in 2016, he is not only a credible vice-presidential candidate, but as a former presidential contender he's already been vetted by national media.

Picking Rubio might reassure voters worried about Trump’s loyalty demands, given his sharp criticism of Trump in 2016 and his vote to certify Biden’s election in 2020. It would signal Trump wants to govern in the national interest, not just in his interests.

Trump's history suggests his top priority will be picking an unquestioning loyalist, such as Vance, who fits that bill better than Rubio.

But in choosing fealty over credibility, Trump would do himself (and the nation) more harm than good.

Christopher J. Devine is an associate professor of political science at the University of Dayton. He is the author of "Do Running Mates Matter? The Influence of Vice Presidential Candidates in Presidential Elections” (with Kyle C. Kopko) and “I’m Here to Ask for Your Vote: How Presidential Campaign Visits Influence Voters.”

This article originally appeared on The Columbus Dispatch: There's a big problem with Trump picking Vance, Donalds or Carson VP