In a letter to the Arizona lawmaker, which was first obtained by POLITICO, 70 Democratic donors — some of whom gave Sinema’s 2018 campaign the maximum contribution allowed by law — said they will support a primary challenge to Sinema and demanded that she refund their contributions to her 2018 campaign if she doesn’t budge.

“We are terrified about our prospects as a democracy if we do not pass the Freedom to Vote Act and John Lewis VRA Act,” they wrote in the 1,400-word missive. “We appreciate your support of these bills, but they will die without your action on Senate rules. Bipartisanship works only if it is reciprocal. Republicans are gutting our electoral system in state capitals with no federal check on them. This is life and death important to us.”…

“I can’t recall this kind of pressure coming from party regulars,” said Adam Jentleson, a Democratic strategist who supports eliminating the filibuster and wrote the book “Kill Switch: The Rise of the Modern Senate and the Crippling of American Democracy.” “I think it says a lot that there’s this level of feeling right now.”