SACRAMENTO, Calif. (AP) — Two California Democrats said Thursday they'll bring back legislation that would require presidential candidates to release their tax returns before they could appear on the ballot in the largest U.S. state.

Gov. Jerry Brown vetoed similar legislation last year, saying he was concerned it was unconstitutional and might open the door to other litmus tests for candidates.

The bill is aimed at forcing President Donald Trump to release his tax returns if he runs for re-election in 2020 and to ensure future candidates will reveal theirs. Trump bucked tradition and did not publish his taxes during his 2016 campaign.

The lawmakers, Democratic Sens. Mike McGuire of Healdsburg and Scott Wiener of San Francisco, said that they decided to bring back their legislation following Trump's summit this week with Russian President Vladimir Putin.

The summit raised questions about Trump "cozying up to the Russian dictator," McGuire said in a statement.

"There is one definitive way to bring to light any potential financial and legal conflicts of interest that could drive an American president into the arms of a hostile foreign power — that's making Trump's tax returns public," McGuire said.

Tax returns reveal income sources, charitable giving, exemptions and other financial information. Trump said he did not want to disrupt an ongoing federal audit of his returns by releasing them.

Opponents of the disclosure bill questioned whether it could be enforced, arguing the U.S. Constitution already outlines the qualifications to be president. Democratic office holders, though, have argued that states have the power to determine ballot access.