Washington (CNN) Rep. Adam Schiff on Wednesday introduced a constitutional amendment to overturn the Supreme Court's Citizens United decision, which helped usher in a new era of big money in American elections.

"Our democracy is not for sale. We must stop the flood of dark money from drowning out the voices of everyday citizens," the California Democrat said in a statement on Twitter. He said such an amendment would "restore power to the American people."

By a 5-4 ruling, the high court in 2010 swept aside a ban on independent spending by corporations and unions in candidate elections, saying the restrictions amounted to censorship. Outside spending in federal elections has soared from $338 million in 2008, the last presidential election before the ruling, to $1.4 billion in 2016, according to the nonpartisan Center for Responsive Politics.