We need to be prepared for Trump dumping JD Vance right after the Democratic Convention and replacing him

[Ocelot II]

36. Dumping Vance would be an admission that he'd made a mistake.

TFG doesn't admit making mistakes; he doubles down. And even if he did unload him, it would open him up to criticism that he and his campaign don't know what they're doing. That's what happened when McGovern dumped Eagleton after the Dem primary in 1972 after learning that he had been treated for depression:

McGovern initially supported Eagleton... and stated publicly, "I am 1,000 percent for Tom Eagleton and have no intention of dropping him from the ticket." Though many people still supported Eagleton's candidacy, an increasing number of influential politicians and newspapers questioned his ability to handle the office of vice president and, potentially, president or questioned the McGovern campaign's ability to survive the distraction. The resulting negative attention ... prompted McGovern to accept ... Eagleton's offer to withdraw from the ticket. It remains the only time a major party vice presidential nominee has been forced off the ticket. Five prominent Democrats then publicly turned down McGovern's offer of the vice presidential slot: in sequence, Kennedy again, Abraham Ribicoff, Humphrey, Reubin Askew, and Muskie. .. Finally, he named United States ambassador to France Sargent Shriver... McGovern's 1,000 percent statement and subsequent reneging made him look both indecisive and an opportunist, and has since been considered one of the worst gaffes in presidential campaign history. McGovern himself would long view the Eagleton affair as having been "catastrophic" for his campaign.

https://en.wikipedia.org/wiki/George_McGovern