Sen. Bernie Sanders went after moderate Democrats Sens. Joe Manchin, D-W.Va., and Kyrsten Sinema, D-Ariz., on Twitter Monday, pressuring the two members of Congress to help their party change the Senate’s rules in order to get election and voting reforms passed through Congress.

“As the voting rights bill finally comes to the floor of the Senate, there is only one vote which will really matter,” Sanders wrote on Twitter. “Will 50 Democrats vote to override the filibuster, protect American democracy and pass the bill, or will Manchin and Sinema vote with the GOP and let the bill die?”

As a result of failing to get election and voting reform legislation through Congress, Democrats have begun seeking to change the Senate rules to squash the 60-vote threshold, known as the filibuster, which has been standing in their way.

Without the filibuster rule being changed the Senate is at an even 50-50 split, with Vice President Kamala Harris being the deciding vote in a simple majority. Most votes today, however, require a supermajority of nearly two-thirds of the senators, 60 votes, for most legislation to pass.

President Joe Biden said in an interview with ABC News last month that he supports making an exception to the filibuster rule in order to get Democrats’ voting and election reform legislation through Congress.

However, Manchin and Sinema have both expressed their unwillingness to support such an exception to the Senate rules, according to CNN, which could potentially be changed with a simple majority of senators.

Without Sinema and Manchin, the rule change appears to be out of reach for Democrats.

“Make no mistake, the United States Senate will — for the first time this Congress —debate voting rights legislation beginning on Tuesday,” Senate Majority Leader Chuck Schumer said last Thursday. “Members of this chamber were elected to debate and to vote, particularly on an issue as vital to the beating heart of our democracy as this one. And we will proceed."