Former Sen. Russ Feingold (D-Wis.) says he is increasingly optimistic that the Supreme Court will act to reverse the Citizens United ruling that rolled back limits on campaign spending.  

Feingold has long been an opponent of the ruling, which cleared the way for corporations and unions to spend unlimited amounts of money to influence elections as long as there is no coordination with campaigns.

"I think there's all kinds of signs that the justices are getting squeamish — that they know they've done something even worse than Bush v. Gore in terms of the credibility of the court," Feingold said Wednesday on "The Bill Press Show."

"The credibility of the court is greatly diminished because of this, and I'm getting more optimistic that something's going to happen about this decision at some point," Feingold continued.

Feingold was the co-author — with Sen. John McCain (R-Ariz.) — of the McCain-Feingold campaign finance law, which limited the amount of money individuals could donate to political campaigns. The Citizens United ruling struck down a portion of that law, saying Congress should not be allowed to put limits on independent corporate spending, spending by unions, or other, similar entities.

Feingold criticized President Obama earlier this month for backing a super-PAC that supports his reelection bid, saying the president was "dancing with the devil."