Former Democratic Sen. Joe Manchin called out Republican John Cornyn over his flip-flop on nuking the filibuster, using the Texas Senate candidate's own words against him in a lengthy post to social media.Previously serving as a Senator for West Virginia, Manchin made headlines throughout Joe Biden's presidency for his opposition to more progressive policy proposals, earning him widespread condemnation for holding back the former president's agenda. One position he held strong to during that period was his opposition to ending the filibuster, an idea many Democrats floated to help overcome Republican resistance to their legislation.This week, Cornyn, a Texas representative running in a heated GOP primary for the Senate, reversed his own past opposition to ending the filibuster. This came as Donald Trump has pushed hard for filibuster reforms to help pass the SAVE America Act, a bill meant to address his long-debunked claims of widespread voter fraud. Cornyn made the reversal as he is competing for Trump's endorsement in his primary, where he is currently polling neck-and-neck with scandal-plagued Texas Attorney General Ken Paxton.In a lengthy post to his official X account, Manchin decried Cornyn's flip-flop and did so by quoting the congressman himself when he spoke out against Democrats pushing to nuke the filibuster. "They'll soon find themselves rueing the day their party broke the Senate," Cornyn said, as quoted by Manchin."When I was a U.S. Senator, there was not another person more committed to keeping the filibuster than Senator John Cornyn," Manchin wrote. "He understood the incredible political pressure I faced from my former party to get rid of the filibuster and give Democrats complete power — and at the time, he understood why neither party should take our country past this point of no return."He added: "It’s deeply disappointing to see that Senator Cornyn is now willing to scrap the very rule he once praised and personally thanked me for defending. These extreme election-year politics that put party power over everything else are why Americans are sick and tired of the duopoly of the two-party system of Democrats and Republicans."Senate Majority Leader John Thune has so far held firm against a massive pressure campaign to go around the filibuster rules to get the SAVE Act passed by a simple majority. He has warned that the votes to accomplish such a move are not there and that Democrats could take advantage of the changes to grind the chamber to a halt.