EXPERT THINKS J.D. VANCE IS THE VP PICK:

The three reported finalists for vice presidential nominee are Florida Sen. Marco Rubio, North Dakoka Gov. Doug Burgum and Ohio Sen. J.D. Vance.

Christopher Devine, an associate political science professor at the University of Dayton, has written two books on the impact running mates have on a ticket.

Devine said vice presidential candidates can influence voters by providing a boost based on geography or demographics. For instance, a running mate night help deliver their home state, while a woman or candidate of color might rally voters who see themselves in the V.P. nominee.

However, Devine said those affects tend to be minimal. A more significant impression the running mate leaves is as a reflection of the presidential candidate’s judgement.

“Who they pick tells you something about their priorities in politics,” Devine said. “It tells you about how serious they are in terms of the decisions that they make.”

Devine said a V.P. nominee is most impactful when the presidential candidate isn’t particularly well-known, pointing to the 2008 campaign when voters who didn’t closely follow politics probably didn’t know much about either Barack Obama or John McCain.

He said polling showed voters thought less of McCain’s judgement after he picked Sarah Palin as his running mate. Palin, and her series of speaking gaffes, contrasted with Obama’s running mate, then-longtime Senator Joe Biden.

Well, that’s not a mark in favor of voters’ judgment.