Washington (CNN) - Saying that "No one should be able to pump unlimited funds into political campaigns, whether they are Democrat, Republican or independent," Senate Majority Leader Harry Reid on Thursday strongly backed a proposed constitutional amendment that would limit campaign spending by outside groups.
Reid announced on the Senate floor that the Judiciary Committee would soon hold a hearing on the amendment, introduced earlier this year by Democratic Sens. Tom Udall of New Mexico and Michael Bennet of Colorado, and that the full "Senate will vote on that legislation."
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The measure would curb unlimited campaign spending by giving Congress the authority to regulate raising and spending limits for federal elections.
"Sens. Udall and Bennet's amendment reins in the massive spending of super PACs which have grown so much since the Citizens United decision," Reid added.
That's the 2010 Supreme Court ruling that removed legal barriers preventing corporations and unions from spending unlimited sums on federal elections.
The amendment should likely pass the Judiciary Committee, where it only needs a simple majority to advance. But its chances of passing the full Senate, where it needs a two-thirds majority, are extremely slim, due to broad GOP opposition.
As he has numerous times the past few months, Reid targeted much of his firepower against the billionaire industrialists David and Charles Koch, who have spent hundreds of millions since 2010, through the conservative non-profit political advocacy group Americans for Prosperity and other organizations, to attack Democrats and support Republicans. Overall, pro-GOP outside groups have heavily outspent their pro-Democratic rivals since the 2010 Supreme Court ruling opened the floodgates.
"There is absolutely no question the Koch brothers are in a category of their own, in both degree and kind. No one else pumping money into the shadowy campaign organizations and campaigns like they are. There isn't even a close second," Reid said. "They are doing this to promote issues that make themselves even richer."
"Why not level the playing field for everyone. Let's get this money out of our political system. Let's undo the damage done by the citizens united decision. Let's do it now," the Democrat from Nevada added.
Republicans were quick to fire back at Reid's move.
"Today's proposal by the Senate Majority Leader represents an all-out assault on the right to free speech, a right which undergirds all others in our democracy. It's also a clear sign of just how desperate elected Washington Democrats have become in their quest to hold onto power," Senate Minority Leader Mitch McConnell said in a statement.
"Proposing to take away this fundamental right from the American people and vest it in the federal government instead is the ultimate act of radicalism, and it should concern all Americans who care about their right to speak their minds and to participate freely in the political process," added the five-term senator from Kentucky who faces a tough-election of his own this year.
Reid's comments on Capitol Hill came at the same time that American Bridge, a pro-Democratic outside group that concentrates on opposition research against Republicans and defends Democrats, announced a new research and rapid-response project aimed at the Koch brothers.
While Democrats point to the Koch brothers as the poster boys for what they term out-of-control outside spending, Republicans point to Tom Steyer, the wealthy hedge fund manager, philanthropist, and environmentalist, who has bankrolled many Democratic outside efforts.
At play is control of the Senate. The Democrats hold a 55-45 majority in the chamber (including two independents who caucus with the party). But the party's defending 21 of the 36 seats in play in this November's midterm elections, with half of those Democratic-held seats in red or purple states.
Americans for Prosperity has already spent around 25 million to attack Democrats and support Republicans in key Senate races so far this cycle. The biggest pro-Democratic spending outside group, Senate Majority PAC, has shelled out $11.1 million.
While the constitutional amendment faces all-but-certain defeat on the Senate floor, Democrats believe public opinion is on their side, and that the efforts to push the amendment could motivate their base, which is crucial in traditionally low-turnout midterm contests.
Reid first signaled his support of the Udall-Bennet amendment in a BuzzFeed report Wednesday.
The issue of campaign spending was also in the Supreme Court's spotlight earlier this spring. A 5-4 ruling last month by the justices eliminated limits on how much money individuals can donate in total in one election season.
However, the decision left intact the current $5,200 limit on how much an individual can give to any single candidate during a two-year election cycle. Until now, an individual donor could give up to $123,200 per cycle.
The ruling means a wealthy donor can give as much money as desired to federal election candidates across the country, as long as no candidate receives more than the $5,200 cap.