By Eugene Scott

CNN

(CNN) -- A Democratic lawmaker said he's open to conversations about preserving the filibuster to prevent Republicans from using "the nuclear option" to fill a Supreme Court vacancy.

After four Senate Democrats announced Monday they plan to oppose Neil Gorsuch, the Democratic caucus reached the 41 votes needed to sustain a filibuster against the Supreme Court nominee. The announcement sets Republicans up to change Senate rules -- referred to as the "nuclear option" -- to lowering the threshold of advancing Supreme Court nominees to just 51 votes from 60.

"I'm not digging in. I'm saying I am open to conversations about how we might preserve the filibuster," Sen. Chris Coons told CNN's Alisyn Camerota Tuesday on "New Day." "It is clear to the Republican majority -- if they choose to break the rules, to change the rules -- that will be on them."

The Delaware Democrat added: "There are Democrats and Republicans who I hope will be talking this week, in the next two days, to see if we could find some path forward where we preserve the filibuster."

Republicans argue that the controversial move is their only choice. Invoking the "nuclear option" would permanently nix the filibuster for Supreme Court nominees, essentially giving the party in power all the leverage and eliminating the Senate's tradition of needing at least some bipartisanship to advance such nominees.

Sen. John McCain, R-Arizona, called the decision to use the tactic "a dark day" in American history.

"I think it's a dark day in the history of the United States Senate. It's going to happen," he told Camerota Tuesday. "It's interesting that Republicans were dead set against it when my former colleague (Nevada Democrat) Harry Reid invoked it with the judges (in 2013), but now it seems to be OK."

"Now we're so polarized now, including between the two leaders, (Republican) Mitch McConnell and (Democrat) Chuck Schumer that there's no communications anymore," McCain added.