House Democrats are set to introduce legislation Wednesday calling for a formal probe into Russian cyber hacking in the 2016 election, part of a broader Democratic push to shed light on unprecedented foreign interference in a US voting season.

Leading national security Democrats in the House also asked the White House on Tuesday to share classified information on Russian hacking with Congress, saying in a letter that Moscow “may have succeeded in weakening American’s trust.”

“We are deeply concerned by Russian efforts to undermine, interfere with and even influence the outcome of our recent election,” said the letter, signed by Adam Schiff, the most senior Democrat on the House Permanent Select Committee on Intelligence, and six others. “By eroding Americans’ and foreigners’ trust in US institutions, Russia both weakens our country and sows global instability and uncertainty.”