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

After cutting some memorable campaign commercials for now-Sens. Ben CardinBenjamin (Ben) Louis CardinSenate Democrats aim to repeal rules blocking Trump tax law workarounds Congress briefed on Iran after Saudi oil attacks Senate Democrats hesitant to go all-in on impeachment probe MORE (D-Md.) and Claire McCaskillClaire Conner McCaskillIranian attacks expose vulnerability of campaign email accounts Ex-CIA chief worries campaigns falling short on cybersecurity Ocasio-Cortez blasts NYT editor for suggesting Tlaib, Omar aren't representative of Midwest 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.