The U.S. Senate's most moderate female Republican is helping Sen. Pat Toomey make an appeal to suburban Philadelphia women, a voting bloc crucial in the close Pennsylvania race.

Maine Sen. Susan Collins held up Toomey on Tuesday as an independent thinker who's made extraordinary efforts to break partisanship.

Toomey is one of the Senate's most vulnerable Republicans. He's being challenged by Democrat Katie McGinty.

Toomey needs to persuade Democrats to split their votes and win independents to overcome the roughly double-digit advantage Democratic presidential nominee Hillary Clinton holds over Republican Donald Trump.

Toomey has distanced himself from the GOP presidential nominee and on gun control from his party, but Toomey hasn't ruled out voting for or endorsing Trump.

McGinty said Toomey's "talking out of both sides of his mouth."