Senate leaders are planning a floor vote on the GOP tax reform measure potentially as soon as Thursday, according to Bloomberg News.

Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellGraham: GOP will confirm Trump's Supreme Court nominee before the election Trump puts Supreme Court fight at center of Ohio rally The Memo: Dems face balancing act on SCOTUS fight MORE (R-Ky.) has long said he intended to have the $1.4-trillion package of tax cuts on the floor the week after Thanksgiving — a timeline intended to get the measure to President Trump’s desk before the end of the year.

Republicans have struggled to give Trump a signature legislative achievement to sign his name to during the first year of his presidency, after several failed attempts to unravel Obamacare, and the pressure is on now.

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But the GOP must hold together a razor-thin 52-vote majority in order to overcome the united opposition of Democrats, who argue that the bill only benefits wealthy Americans.

The House passed its version of the legislation last week — featuring several marked differences from the Senate bill — but its victory in the upper chamber is by no means certain.

Several Republican senators — like Sens. Bob Corker Robert (Bob) Phillips CorkerHas Congress captured Russia policy? Tennessee primary battle turns nasty for Republicans Cheney clashes with Trump MORE (Tenn.), Jeff Flake Jeffrey (Jeff) Lane FlakeJeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Republican former Michigan governor says he's voting for Biden Maybe they just don't like cowboys: The president is successful, some just don't like his style MORE (Ariz.), James Lankford James Paul LankfordMcConnell works to lock down GOP votes for coronavirus bill Charities scramble to plug revenue holes during pandemic Warren calls for Postal Service board members to fire DeJoy or resign MORE (Okla.) and John McCain John Sidney McCainBiden's six best bets in 2016 Trump states Replacing Justice Ginsburg could depend on Arizona's next senator The Hill's Morning Report - Sponsored by Facebook - Washington on edge amid SCOTUS vacancy MORE (Ariz.) — have raised concerns about the $1.4 trillion that the Joint Committee on Taxation says the bill will add to the federal deficit, contrary to supporters’ claims that the tax cuts will generate enough economic growth to pay for themselves.

Sen. Ron Johnson Ronald (Ron) Harold JohnsonThis week: Supreme Court fight over Ginsburg's seat upends Congress's agenda GOP set to release controversial Biden report Democrats fear Russia interference could spoil bid to retake Senate MORE (R-Wis.) has raised objections to the way the bill treats small businesses. Sen. Susan Collins Susan Margaret CollinsGraham: GOP will confirm Trump's Supreme Court nominee before the election Gardner signals support for taking up Supreme Court nominee this year Tumultuous court battle upends fight for Senate MORE (R-Maine) has taken issue with a provision repealing the so-called “individual mandate” in Obamacare. (Senate tax writers are leaning on cutting the mandate as a critical part of funding the tax cuts.)

Sen. Lisa Murkowski Lisa Ann MurkowskiGraham: GOP will confirm Trump's Supreme Court nominee before the election Gardner signals support for taking up Supreme Court nominee this year Tumultuous court battle upends fight for Senate MORE (R-Alaska), who had previously expressed reservations, provided a boost to the bill’s chances this week when she said that she would support axing the individual mandate.

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GOP leaders can afford to lose only two votes before the legislation sinks.

If the bill clears the Senate by Thursday — a dramatic moment that is likely to come after marathon debate — the two chambers will have to hammer out discrepancies in the legislation.

Major differences include timing and permanence of the tax cuts — something House Speaker Paul Ryan Paul Davis RyanKenosha will be a good bellwether in 2020 At indoor rally, Pence says election runs through Wisconsin Juan Williams: Breaking down the debates MORE (R-Wis.) has blamed on Senate rules — and its treatment of the Affordable Care Act.

The tax bill “needs work,” Collins said earlier this week, according to Bloomberg. “I think there will be changes.”