If corporate and union officials want to pour money into election campaigns, they would have to disclose who they are -- and perhaps appear in an ad -- under legislation introduced in Congress on Thursday.

The bill is a response to a controversial U.S. Supreme Court decision allowing unlimited corporate and interest group spending on elections. In Citizens United vs. the Federal Elections Commission, the court in January struck down most federal limits on corporate spending as a violation of free speech.

Sen. Charles E. Schumer (D-N.Y.), in an announcement at the steps of the Supreme Court, said the measure would “shine a light on the flood of spending unleashed by the Citizens United decision.”

He hopes to win passage of the bill by July 4, in time for any flow of corporate money into the 2010 midterm congressional elections.

Schumer said “a good number” of Republicans “are very favorably disposed to the legislation,” but none appeared with him.

Senate Minority Leader Mitch McConnell (R-Ky.) called Schumer’s announcement “beyond suspicious,” and charged that the bill is “about election advantage, plain and simple.”

Two Republicans cosponsor the House version of the bill, which would require the chief executive or head of an organization that is the primary financial sponsor of a televised political ad to take responsibility for it by appearing on camera. Corporations, unions and advocacy groups would be required to create traceable campaign accounts and disclose -- via the Web and corporate filing statements -- the source of donations exceeding $1,000.

The bill also would ban expenditures by government contractors and any domestic corporation if at least 20% of its stock was owned by foreign nationals, or if foreign nationals played a dominant role in the corporation’s leadership.

Companies that received federal bailout funds would be barred from making expenditures until they repaid those funds. Republican Reps. Michael N. Castle of Delaware and Walter B. Jones of North Carolina joined Democratic Rep. Chris Van Hollen of Maryland in introducing the House version of the bill.

“I don’t see why this issue is a partisan one that should divide us,” Castle said. “This is a serious attempt to have disclosure.”

But Richard L. Hasen, a professor at Loyola Law School in Los Angeles who specializes in election law, said the bill faces political and legal hurdles: It must pass a heavily divided Senate in the midst of an election year, and it would probably face a Supreme Court challenge.

“It is unclear whether this Supreme Court, which has shown a lot of hostility to campaign finance regulation, would be willing to uphold this,” Hasen said.

William J. McGinley, a Republican lawyer, said the bill was “carefully tailored to protect the Democratic majority in Congress and their soft-money allies, the unions.”

President Obama praised the measure. “I welcome the introduction of this strong bipartisan legislation to control the flood of special-interest money into America’s elections,” he said.

Democrats have been concerned that the Citizens United ruling could give the GOP an unfair advantage, because major corporations tend to support Republicans. The GOP counters that Democrats enjoy the favor of powerful labor unions, also big political spenders.

Schumer said the bill would “stop the funneling of big money from shadow groups in order to fund ads that are virtually anonymous,” a reference to organizations such as the U.S. Chamber of Commerce.

Chamber President and Chief Executive Thomas Donohue called the bill “a thinly veiled attempt to hijack the political playing field ÃÂ on the eve of midterm elections.” Republicans have hopes of retaking control of Congress in November.

kim.geiger@latimes.com

clement.tan@latimes.com