Gov. Jerry Brown cleared the way Wednesday for Californians to vote in November on whether to urge their congressional representatives to approve a constitutional amendment repealing the U.S. Supreme Court’s Citizens United decision, which allowed corporations to spend unlimited amounts on political campaigns.

The state Supreme Court blocked a similar ballot measure in 2014, saying it wasn’t clear whether state law allowed advisory measures on the ballot, but ruled this January that voters could consider the proposal if the Legislature approved it again. Lawmakers, voting mostly along party lines, then passed SB254 by Sen. Ben Allen, D-Santa Monica, and Brown, who could have signed or vetoed the measure, said Wednesday he had allowed it to proceed toward the ballot without his signature.

Opponents said the nonbinding measure was intended mainly to boost turnout among Democratic voters.

The Supreme Court ruled 5-4 in 2010 that corporations and labor unions had a constitutional right, protected by freedom of speech, to spend money from their treasuries on campaigns. They remain limited by law in the amounts they can contribute to candidates, but can donate unrestricted amounts to independent campaign committees.

Legislatures in several states, including California, have voted to urge Congress to pass a constitutional amendment that would overturn the ruling. But the message would mean more if it came from the voters, said Trent Lange, president of the California Clean Money Campaign. He said voters in Colorado and Montana have approved measures like the one headed for the California ballot.

The proposed amendment would go beyond repealing Citizens United and declare that “corporations aren’t people and money isn’t speech,” Lange said. He said it would be drafted so as to preserve freedom of the press for news media corporations.

Such an amendment would overturn multiple Supreme Court rulings “that have allowed money to dictate policy and left the people without a voice,” said Michele Sutter, leader of another advocacy group, Money Out Voters In.

Constitutional amendments require approval by two-thirds of each house of Congress and ratification by legislatures in three-fourths of the states.

Bob Egelko is a San Francisco Chronicle staff writer. Email: Twitter: egelko