COCONUT CREEK, Fla. - Spare a thought for Donald Trump -- Hillary Clinton barely did as she began a visit today to America's biggest swing state.

Increasing Democratic confidence about winning the White House has prompted a late-campaign recalibration as the party shifts its sights toward the new target of winning back power in Congress.

Clinton spent the first five minutes of a Florida speech lacing into Republican senator Marco Rubio, urging her college audience to instead elect Democrat challenger Patrick Murphy.

She says Murphy shares their values on issues like climate change, economic equality, immigration reform and lighter prison sentences.

She also says that unlike his opponent Rubio, Murphy "has never been afraid to stand up to Donald Trump."

While Clinton is the overwhelming favourite in the presidential race, the same polls that show her winning in swing states like Florida show her party's candidate trailing in some of the same places.