I think it would be a huge mistake on his part, especially if he’s down in the polls.  But a number of pundits think he will do just that.

McCain’s granddaughter voting for Clinton.

Romney feels lost.

Trump responds to the father of slain soldier by saying that he’s made sacrifices too by working hard.

Republican voter-suppression laws have been defeated in three states.

This poll, by a firm I’m not familiar with, indicates a huge bounce for Clinton, but I have a hard time believing it that she can have a 15 point lead over Trump and still not break 50 percent.  That’s a lot of third party/undecideds. The article doesn’t indicate the dates the polling was performed.

Addendum:  I am very familiar with PPP, and they have good news for Clinton.

On the above-linked RABA poll, apparently Nate Silver rates them “B+”

Second addendum:  I guess this is a big thing – Houston paper which usually endorses Republicans coming out with a very early endorsement of Clinton – or anti-endorsement of Trump anyway.

Third addendum:  So in a third poll, it’s clear Clinton got her “bounce.”  As to what it means for the long term?  Again, I don’t think she’s going to look back.  We’ll see.  This polls as Gary Johnson at about twice the numbers of other polls, and apparently they didn’t bother to ask about Jill Stein, so I question the poll on a number of levels.  Still, what polls are effective in detecting is movement, regardless of the snapshot accuracy.