Sen. Lindsey Graham Lindsey Olin GrahamLincoln Project mocks Lindsey Graham's fundraising lag with Sarah McLachlan-themed video The Hill's Morning Report - Sponsored by Facebook - Republicans lawmakers rebuke Trump on election Trump dumbfounds GOP with latest unforced error MORE (R-S.C.) said on Friday that all but three GOP senators had signed onto his resolution condemning the House impeachment inquiry.

GOP Sens. Susan Collins Susan Margaret CollinsDemocratic senator to party: 'A little message discipline wouldn't kill us' Poll: 57 percent of Americans think next president, Senate should fill Ginsburg vacancy On The Trail: Making sense of this week's polling tsunami MORE (Maine), Lisa Murkowski Lisa Ann MurkowskiDemocratic senator to party: 'A little message discipline wouldn't kill us' Overnight Energy: Trump officials finalize plan to open up protected areas of Tongass to logging | Feds say offshore testing for oil can proceed despite drilling moratorium | Dems question EPA's postponement of inequality training Poll: 57 percent of Americans think next president, Senate should fill Ginsburg vacancy MORE (Alaska) and Mitt Romney Willard (Mitt) Mitt RomneyCrenshaw looms large as Democrats look to flip Texas House seat The Hill's Morning Report - Sponsored by Facebook - Republicans lawmakers rebuke Trump on election Trump dumbfounds GOP with latest unforced error MORE (Utah) have not yet signed onto the resolution, according to an updated list of co-sponsors shared by Graham the day after he introduced the measure.

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A spokesperson for Collins didn't immediately respond to a request for comment about whether or not she would back the resolution.

A spokeswoman for Romney noted that he said on Thursday that he would look at the resolution.

"I’d like to see a vote taken in the House to decide whether there is support for impeachment. I’d love to see a more open process," Romney said.

Murkowski also told reporters on Thursday that she hadn't yet read the resolution, which formally opposes the impeachment inquiry and urges House Democrats to hold an official vote on it.

The resolution also says the House should give President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE "due process" including "the ability to confront his accusers" and that House Republicans should be able to subpoena their own witnesses.

When Graham introduced the resolution, he had 39 co-sponsors, but that quickly ticked up to 44, with only nine Republicans not signed on as of Thursday afternoon: Romney, Collins, Murkowski and Sens. Cory Gardner Cory Scott GardnerBreaking the Chinese space addiction Trump dumbfounds GOP with latest unforced error Billionaire who donated to Trump in 2016 donates to Biden MORE (Colo.), Lamar Alexander Andrew (Lamar) Lamar AlexanderPelosi urges early voting to counter GOP's high court gambit: 'There has to be a price to pay' Graham: GOP has votes to confirm Trump's Supreme Court nominee before the election The Hill's Morning Report - Sponsored by Facebook - Washington on edge amid SCOTUS vacancy MORE (Tenn.), Mike Enzi Michael (Mike) Bradley EnziChamber of Commerce endorses McSally for reelection Cynthia Lummis wins GOP Senate primary in Wyoming The Hill's Convention Report: Democrats gear up for Day Two of convention MORE (Wyo.), Dan Sullivan Daniel Scott SullivanOvernight Energy: Trump officials finalize plan to open up protected areas of Tongass to logging | Feds say offshore testing for oil can proceed despite drilling moratorium | Dems question EPA's postponement of inequality training Trump administration finalizes plan to open up protected areas of Tongass National Forest to logging OVERNIGHT ENERGY: House passes sweeping clean energy bill | Pebble Mine CEO resigns over secretly recorded comments about government officials | Corporations roll out climate goals amid growing pressure to deliver MORE (Alaska), Johnny Isakson Johnny IsaksonDemocrats ramp up pressure on Lieberman to drop out of Georgia Senate race Obama endorses Warnock in crowded Georgia Senate race Lobbying world MORE (Ga.) and Rob Portman Robert (Rob) Jones PortmanMcConnell locks down key GOP votes in Supreme Court fight Romney undecided on authorizing subpoenas for GOP Obama-era probes Congress needs to prioritize government digital service delivery MORE (Ohio).

Graham tweeted early Thursday evening that Portman and Sullivan had signed on as co-sponsors, while Alexander, Isakson, Gardner and Enzi were in the list of co-sponsors released by Graham on Friday.

Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellDemocratic senator to party: 'A little message discipline wouldn't kill us' House to vote on resolution affirming peaceful transition of power Republican lawyers brush off Trump's election comments MORE (R-Ky.), who supports the resolution, has not said if it will come up for a vote. If it did, it would currently fail to overcome a procedural hurdle that requires legislation get 60 votes in order to advance on the Senate floor.

Republicans have fumed over the House impeachment inquiry, which has held near-daily closed-door depositions with current and former administration officials.

Speaker Nancy Pelosi Nancy PelosiDemocratic senator to party: 'A little message discipline wouldn't kill us' Overnight Health Care: New wave of COVID-19 cases builds in US | Florida to lift all coronavirus restrictions on restaurants, bars | Trump stirs questions with 0 drug coupon plan Overnight Defense: Appeals court revives House lawsuit against military funding for border wall | Dems push for limits on transferring military gear to police | Lawmakers ask for IG probe into Pentagon's use of COVID-19 funds MORE (D-Calif.) has said a formal vote for the inquiry isn't required. Republicans, however, want a vote because it would put swing-district Democrats on the record and give them more leverage to call their own witnesses.

Neither Collins, who is up for reelection next year, nor Murkowski nor Romney has backed the House impeachment inquiry or removing Trump from office.

But they've each refrained from taking a position, or chided colleagues who have already made a decision on impeachment.

"I'll keep an open mind until and unless there is some kind of decision reached by the House. ... It's a purposeful effort on my part to stay unbiased, and to see the evidence as it's brought forward," Romney told reporters in Utah earlier this month.

Murkowski, speaking during a recent health care event in Alaska, said it was “troubling ... that even before there has been any considered review, that people have decided.” Meanwhile, Collins said it was "entirely inappropriate" for colleagues to have already "made up their minds."

—Updated at 4:29 p.m.