Twitter said on Tuesday it supports legislation that would force social media firms like Facebook and Twitter to disclose the funding of political ads on its platform.

Twitter’s announcement came just hours before Mr. Zuckerberg’s appearance. Facebook has also endorsed the Honest Ads act and it is expected to be discussed at length during the hearings. The legislation, introduced by Democratic Senators Amy Klobuchar of Minnesota and Mark Warner of Virginia, and Republican Senator John McCain of Arizona, would hold internet companies to the same disclosure rules that broadcast companies have to follow when airing political ads.

The legislation is seen as the most likely — and least intrusive — action to come from Mr. Zuckerberg’s grilling before Congress on Facebook’s mishandling of data. The online political ad disclosures bill was introduced after the revelations of Russian interference in the U.S. presidential election of 2016.