The GOP senator wants to block transfers to "terror hotspots."
A progressive Jewish political action committee is intervening in Senate races for the first time.
"I'm kind of glad they're doing it, but it's so foolish,” he said.
McCain's running in an unpredictable presidential year, with voters angry with Washington.
The controversial politician made a run for the same spot in 2010.
Democrats quickly pounced on his comments.
"The tough thing about these senatorial jobs is you get yes or no votes," he said.
Clinton has gotten pushback for comments made during a CNN townhall.
Katie McGinty is trailing in fundraising and polls against former Rep. Joe Sestak.
The Judiciary chairman says it would be difficult not to accept a meeting.