Senate Democrats have proposed a constitutional amendment aimed at reversing recent Supreme Court decisions that loosened campaign finance restrictions.

The proposal would let state governments and Congress regulate and limit the raising and spending of money for federal political campaigns. The amendment also would grant Congress and states the authority to regulate and limit independent expenditures, such as those from so-called super PACs.

Senate Rules and Administration Committee Chairman Chuck Schumer, D-N.Y., who announced the proposal at a hearing of the panel Wednesday, vowed that the Senate would vote on the measure before the end of the year.

"The Supreme Court is trying to take this country back to the days of the robber barons, allowing dark money to flood our elections," said Schumer, the Senate's No. 3 Democrat. "That needs to stop, and it needs to stop now."

The proposed amendment comes after a Supreme Court decision in early April to strike down the overall limits that wealthy donors can contribute to political campaigns. The McCutcheon v. Federal Election Commission ruling was a victory for anti-regulation conservatives who saw the caps as a restriction on free speech rights.

But Democrats have decried the decision, saying that removing the caps will lead to big-money donors gaining even more influence over elections than they already have, a scenario they say is unfair and will lead to corruption.

The Democratic proposal also is a response to the high court's 2010 Citizens United decision that struck down most limits on corporate and union spending in elections on the grounds they violated First Amendment guarantees of free speech.

The proposed amendment, sponsored by Sen. Tom Udall, D-N.M., wouldn't dictate any specific policies or regulations but instead would give Congress the power to set contribution limits and pass campaign finance reform legislation "that withstands constitutional challenges."

The proposal is unlikely to survive Republican opposition in the Senate, where it would require the support of 67 of the chamber's 100 members. But Democrats see the issue as a political winner heading into November's congressional elections.

"Free and fair elections are a founding principle of our democracy, but the Supreme Court's rulings have ensured that they are now for sale to the highest bidder," Udall said. "It's now crystal clear that we need a constitutional amendment to restore integrity in our election system."