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

After cutting some memorable campaign commercials for now-Sens. Ben CardinBenjamin (Ben) Louis CardinFacebook farce shows lawmaker deviousness, demagoguery Dem senator wants details on Manafort's multiple passports US backs out of global oil anti-corruption effort MORE (D-Md.) and Claire McCaskillClaire Conner McCaskillDemocratic Homeland Security members request additional DHS nominee testimony Senate panel delays vote on Trump’s Homeland Security pick Steve Israel: ‘We had a better time at the DMZ than we’re going to have tonight’ 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.