More than 120 organizations on Thursday urged members of the U.S. House to support a constitutional amendment that aims to reverse the damage done to American democracy by Citizens United, the 2010 Supreme Court ruling that effectively enabled corporations to spend unlimited amounts of money to influence political elections.

Major civil rights, environmental, labor, LGBTQ, and good government groups sent a letter (pdf) to lawmakers, which coincided with a national call-in day for constituents to pressure their representatives in Congress support the measure.

The letter to House members says, "We are writing to urge you to cosponsor H.J.Res. 2, the bipartisan Democracy For All Amendment, which would restore the authority of Congress and the states to set commonsense rules for the raising and spending of money on elections to advance political equality for all Americans."

Constitutional amendments should only be pursued "in the rarest of circumstances," the letter continues—but the high court's widely opposed 2010 ruling in Citizens United and related moves "have pushed America to a tipping point in which big-moneyed interests exert control over all levers of government."

"If the wealthy individuals and concentrations of capital can drown out the voices of ordinary Americans in elections, we cease to be a representative democracy," declares the letter. "America needs to be responsive to the people, not to corporations and special interests, or it is no longer a democratic republic."

Highlighting the significant public opposition to the Citizens United decision, supporters of the letter promoted the call-in campaign on social media with the hashtags #CitizensUnited, #28thAmendment, and #DemocracyForAll:

Introduced in January by Rep. Ted Deutch (D-Fla.), the amendment is co-sponsored by 138 other members of the House. All but one, Rep. John Katko (R-N.Y.), are Democrats. The measure was introduced in the upper chamber by Sen. Tom Udall (D-N.M.) in July and is backed by the other 46 senators who caucus with the Democrats.

"Thanks to Citizens United and other disastrous court decisions, our electoral system—and as a result, our democracy—have reached a crisis point," Udall said in July. "Ever since the Supreme Court ruled to open the floodgates for unlimited corporate spending in our elections, secret special interest money has poured in—and drowned out the voices of the American people."

"Now, citizens are losing faith in our institutions because they have every reason to believe that their government no longer answers to them," he added. "It's time to restore the power of the American people to regulate the out-of-control, secret spending in our elections, and make sure that our elections aren’t put up for sale to the highest bidder."