Senate Minority Leader Chuck Schumer, D-N.Y., has vowed to lead a filibuster to try to block Gorsuch's nomination, and only two Democrats out of the eight needed to side with Republicans so far appear ready to defy Schumer and not support it. Those pair of senators are: centrist Sen. Joe Manchin of West Virginia and Sen. Patrick Leahy of Vermont, a former chairman of the Judiciary Committee who prides himself as an institutionalist protector of Senate rules and tradition, according to Senate GOP aides closely tracking the likely vote tally.

Leahy, however, has since backtracked and said his vote to end a likely filibuster would depend on how Gorsuch responds to follow-up written questions.

Manchin's office has said he will vote with Republicans against a filibuster of Gorsuch even if he decides to vote against him in final passage.

Democrats from red states that voted for President Trump are getting inundated with advertisements from conservative groups trying to hold their feet to the fire and urge them to support Gorsuch.

But so far, most of those Democrats are keeping their powder dry and declining to say how they will vote on overcoming a filibuster or on a final vote to confirm Gorsuch.

Sen. Jon Tester, D-Mont., one of the most vulnerable Democrats from a state Trump won by more than 20 percent, said he has yet to decide how he will vote on Gorsuch and whether he will support a Schumer-led filibuster.

Asked if he has made any decisions on Gorsuch, Tester told the Washington Examiner: "Not yet. I will be — still have some material to review."

He joked that he would decide in "three or four weeks — somewhere in there" before getting serious and saying it would be by the end of the week or beginning of next week.

The vote on Gorsuch is expected to take place late next week before the Senate breaks for a two-week Spring recess.

Sen. Chris Coons, D-Del., another Democrat who has yet to indicate which way he will go on Gorsuch, lamented the partisan nature of the climate on the Supreme Court nominee and more broadly in Washington this year.

Since Schumer announced he would lead a filibuster of Gorsuch last week, a number of key Democratic senators up for re-election in 2018 have either said they are undecided or have declined to make their positions public.

Senate Majority Leader Mitch McConnell, R-Ky., has warned Democrats that he is ready to seat Gorsuch "one way or another" and signaled that he could invoke the nuclear option and eliminate the Senate filibuster for the Supreme Court nominations if Democrats unite against Gorsuch.

Senate Minority Whip Dick Durbin, D-Ill., a week ago said he believed Republicans would not have enough votes to overcome a 60-vote threshold to shut down a filibuster.

Even though he is the chief vote-counter in the Senate, Senate aides say Durbin is not whipping Democrats to back a filibuster but is leaving that role to Schumer.

Meanwhile, support for McConnell to invoke the nuclear option is building among Republicans. Two key centrist GOP senators, who previously opposed blowing up Senate rules to seat presidential nominees, wouldn't rule it out as a way to confirm Gorsuch.

Sen. Susan Collins, R-Maine, on Tuesday said Gorsuch is "eminently well-qualified" and doesn't deserve to be filibustered, as Schumer has vowed to do.

"There are no grounds for a filibuster of Neil Gorsuch," she told reporters Tuesday afternoon.

Asked if she would support a decision by Senate GOP leaders to "go nuclear," Collins said: "I am not eager to see the rules changed so I hope that Democrats do not launch a filibuster against an eminently well-qualified nominee."

"I'm hoping we're not going to get to that point — that's all I want to say," she added.

Sen. John McCain, R-Ariz., another member of that group, on Tuesday also wouldn't commit to opposing any effort by McConnell to invoke the nuclear option on Gorsuch.

"I would address that issue when it arises," McCain said when asked if he would back a Senate rules change to seat Gorsuch.