JD Vance is doing a historically bad job. Don't expect Trump to do anything about it.

Experts often debate the best approach to selecting a vice president: Should one try to balance the presidential candidate's characteristics, experience and regional background? Or should one focus on finding a credible governing partner? But there is almost tacit agreement on one principle: the vice presidential nominee must not harm the candidate. And it seems much easier to take risks with a vice presidential pick – from lack of background checks to lack of presidential preparation to poor campaign skills – than to actually help the candidate.

So far, Donald Trump appears to have failed that test with the selection of Ohio Senator J.D. Vance, whose approval ratings have reportedly officially dropped to the lowest of any vice presidential candidate in modern history. Vance was the choice of a confident candidate who had a good chance of re-election following President Joe Biden's notoriously poor performance during the June 27 debate and positive media coverage following an assassination attempt on July 13. The driving factors behind Vance's selection appear to be his recently sharpened credentials as a Trumpist, particularly his statement about how he would have behaved differently on January 6, 2021 than Mike Pence, Trump's former vice president.

But the race has changed since then. Biden is no longer at the top of the Democratic ticket. And Vance looks particularly troubling compared to Minnesota Governor Tim Walz, whom more Americans view positively than negatively. Vance has been unable – or apparently made no particular effort – to distance himself from controversial statements about gender, abortion and childlessness in the past. For this reason, there has been some speculation about Trump's successor.

It's important to say that the chances of that happening are very slim. But if it were to happen, how exactly would it work? From the perspective of the formal rules of the Republican Party, it's pretty straightforward. The rules set out a similar process for replacing the presidential and vice presidential nominees after the convention; the most likely procedure would be a special meeting of the party's standing committee members. (That's what happened when George McGovern replaced Senator Thomas Eagleton with Sargent Shriver in 1972.)

More complicated is the issue of ballot access—some state deadlines have already passed, and early voting begins in a few states in just a few weeks. These are practical problems that could be solved with some effort. Still, getting the ballots right is important. Although we learned in 2016 that voters are actually casting their ballots for their state's electoral college, choosing the wrong candidate for vice president would be a bad image at best and a potential constitutional confrontation at worst. (If no vice presidential candidate receives a majority of electoral college votes, the Senate will choose the vice president.)

The informal part of the process would be similar in some ways to the top job selection, but different in crucial ways. As with the presidential selection, serious coordination between the parties would be required. As my co-author William Adler and I have found in our work on running mate candidates, the parties play a role in choosing the vice president. Still, the presidential candidate plays a large role in narrowing the choices and making the final decision. This leaves room for all sorts of possibilities as we speculate about what might happen next. Importantly, Trump (or someone else) would have to convince Vance to step down before formal efforts to replace him would even be a realistic possibility.

Then there's the question of who might replace Vance on the ballot. This is where it gets interesting, as there may be infighting between the parties in public and behind the scenes, and tensions within the campaign and between the campaign and the party. Some might theorize that Trump should field politicians from key swing states where the campaign has lost ground – one could go through the list of Republican politicians from Wisconsin, Michigan and Georgia, for example. He could go back to his original list and select Doug Burgum or Marco Rubio, both of whom competed for the presidential nomination and went through national vetting.

He could insist on putting someone from an underrepresented group on the ballot — Nikki Haley, Tim Scott or Vivek Ramaswamy (or Rubio) come to mind as possibilities. Ramaswamy, whose energetic RNC speech addressed some of the party's problems in appealing to minority communities, could be seen as a natural replacement for Vance. He is also young and a loyal, committed supporter of Trump. But he has never held political office. Or Trump could look to some of the women whose names were floated earlier this year — like Sen. Katie Britt, R-Ala., to try to match women's energy in light of Harris' historic candidacy.

These are approaches that Trump could try, If He chose the risky path of replacing the vice presidential nominee—which, again, is quite unlikely. And that's not to say that these measures would even work. Politicians who were passed over on the first ballot may not want to join a slate that has since suffered some setbacks and is no longer considered a safe bet. A vote designed to “appeal” to women, Midwestern voters, or minority voters might not work either. Social science research suggests that these efforts rarely succeed.

A key purpose of the vice presidential nominee, aside from avoiding damage or generating negative publicity, is to highlight the presidential nominee's judgment and values. Since Trump has already been president, most people already have opinions on these factors. Deposing Vance would almost certainly generate negative publicity for the former president, raise questions about his judgment, and draw even more attention to his running mate's missteps and mistakes. It's probably simply too late for Trump to pick someone else. And replacement vice presidential nominees are so rare and so closely associated with campaign disasters like McGovern's in 1972 that it would be difficult to pull off the quiet, low-profile campaign that would have been the wiser strategy in the first place.

This article was originally published on MSNBC.com.