Michael J. Fox cuts ad for Specter

Michael J. Fox is making his return to the midterm elections.

After cutting some memorable campaign commercials for now-Sens. Ben CardinBen CardinTop Dem: 'Risk factor' to extending Iran sanctions in lame duck Senate rejects push to block Saudi arms sale Pentagon: No US aircraft flying during Syrian convoy attack MORE (D-Md.) and Claire McCaskillClaire McCaskillFacebook steps up fight against fake news The Trail 2016: Off the sick bed McCaskill: Trump and Dr. Oz a 'marriage made in heaven' MORE (D-Mo.) four years ago, Fox is back in a new spot for Sen. Arlen Specter (D-Pa.).

"Arlen Specter is moving forward," Fox says. "He's won the battles to double funding for biomedical research, to find cures and to save lives.

"He's smart, tough and always moving forward."

Fox's 2006 midterm ads for Cardin and McCaskill drew plenty of attention, especially after Rush Limbaugh accused him of exaggerating the effects of his Parkinson's disease during the ads.

Specter faces Rep. Joe Sestak (D-Pa.) in the May 18 primary. If he wins there, polls show he would also face a tough match in November, with former Rep. Pat Toomey (R-Pa.) leading.