Sen. Kyrsten Sinema (D-Ariz.) delivered a speech on Thursday in which she reiterated her unwavering support for the filibuster, sparking the ire of those who want Democrats to unilaterally change the rules to enable the party to ram through election-related legislation.

The filibuster, a procedural hurdle that requires three-fifths of senators to agree in order to advance toward a vote, serves as a check on whichever party holds the majority.

While Sinema said that she supports both the Freedom to Vote Act and the John Lewis Voting Rights Advancement Act, she also said that she continues to support the filibuster.

"And while I contintue to support these bills, I will not support separate actions that worsen the underlying disease of division infecting our country," Sinema said. "There's no need for me to restate my longstanding support for the 60-vote threshold to pass legislation."

But some on Twitter strongly condemned the senator.

"@SenatorSinema just put a knife in the heart of Democracy. My heart breaks how easily she was bought to support the Republican coup," tweeted MSNBC terrorism analyst Malcolm Nance.

Keith Olbermann, who in the past has hosted programs on MSNBC, tweeted that Sinema "needs to resign or be removed from office immediately." In another tweet he added, "For whatever reason, @SenatorSinema has become a menace to the continuation of American democracy."

"To be blunt: @SenatorSinema chose her side - and that side is white supremacy. That's who she is. That's what defines her now," another person tweeted.

"Kyrsten Sinema is a monster. A grotesque, opportunistic, lying monster," tweeted Michelangelo Signorile, who hosts a SiriusXM radio show.

Democratic Sen. Joe Manchin of West Virginia is also continuing to stand firm on his support for the filibuster.

"Allowing one party to exert complete control in the Senate with only a simple majority will only pour fuel onto the fire of political whiplash and dysfunction that is tearing this nation apart — especially when one party controls both Congress and the White House," Manchin said in a statement. "As such, and as I have said many times before, I will not vote to eliminate or weaken the filibuster."