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

After cutting some memorable campaign commercials for now-Sens. Ben CardinBen CardinMaking water infrastructure a priority Senators introduce new Iran sanctions Senate confirms Trump's pick for Israel ambassador MORE (D-Md.) and Claire McCaskillClaire McCaskillUnder pressure, Dems hold back Gorsuch support Overnight Defense: General warns State Department cuts would hurt military | Bergdahl lawyers appeal Trump motion | Senators demand action after nude photo scandal The Hill’s Whip List: Where Dems stand on Trump’s Supreme Court nominee 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.