Sen. Charles Schumer, the sponsor of the stalled campaign finance bill, promised Tuesday that Democrats would hold round-after-round of votes on it until it passes. 

Schumer (D-N.Y.) spoke to reporters following the weekly caucus luncheons, slamming Republicans for holding up the response to the Citizens United Supreme Court case, which allowed unlimited political spending by corporations and unions. 

"And we will go back at this bill again and again and again until we pass it," he said. "It's that vital, not to Democrats, not to Republicans, but to the future of people's faith in the functioning of this government."

Schumer made his comments just before the Senate was scheduled to vote to invoke cloture on the measure. The vote was expected to fail.

Sen. Joe Lieberman (I-Conn.) was absent heading into the vote, while centrist GOP Sen. Olympia Snowe (Maine), whose vote was closely watched on the issue, said the bill wasn't in a position yet where she could support it.

The Senate's 59 Democrats need at least one Republican to advance the bill and avoid a filibuster. Unless a Republican comes onboard, Democrats will almost certainly need to make changes to the legislation to win a GOP backer.

Schumer said that the legislation's failure would do harm to the health of U.S. democracy.

"It's the amount of money, not who you are, that is affected. And so we've seen a campaign of desperation, of full muscle, to try to do everything they can to stop this bill because they realize, as already in some campaigns we have seen, how this will fundamentally change the balance of American politics," he said. "It will make the average citizen feel more and more remote from his or her government. It will hurt the fabric of our democracy."