Sen. 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 (R-Ariz.) said on Thursday that he will support the Senate Republicans' tax plan, which GOP leadership wants to pass this week.

“After careful thought and consideration, I have decided to support the Senate tax reform bill. I believe this legislation, though far from perfect, would enhance American competitiveness, boost the economy, and provide long overdue tax relief for middle class families," McCain said in a statement.

McCain added that the Senate legislation would "directly benefit all Americans, allowing them to keep a higher percentage of what they earn."

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McCain's decision is the latest boost to Republicans, after every GOP senator voted to start debate on the legislation Wednesday evening.

It's also a reversal from the ObamaCare repeal effort in July, when McCain joined with GOP Sens. 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 (Maine) and 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 (Alaska) to kill the "skinny repeal" legislation. Murkowski announced on Wednesday that she would back the tax-reform bill.

McCain, at the time, blasted his colleagues for sidestepping the "regular order" and urged them to work together to craft a bipartisan deal on health care.

He praised leadership on Thursday for giving the bill a public markup, where it was passed out of the Finance Committee on a party-line vote.

"I am pleased that this important bill was considered through the normal legislative processes, with several hearings and a thorough mark-up in the Senate Finance Committee during which more than 350 amendments were filed and 69 received a vote," he said.

McCain had dodged for weeks on laying out his position the tax bill. While he spoke positively about it, he had also signaled concerns about the legislation's impact on the deficit — the same reason he voted against the Bush tax cuts in 2001 and 2003.

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Several GOP deficit hawks remain concerned about the impact on the deficit, which the Congressional Budget Office estimated would increase by $1.4 trillion over the next decade.

McCain noted he takes "seriously the concerns" of his colleagues, but thinks the bill will help the economy.

"This is not a perfect bill, but it is one that would deliver much-needed reform to our tax code, grow the economy, and help Americans keep more of their hard-earned money," he said.

Senate 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.) needs 50 of his 52 GOP senators to support the legislation, if every Democrat opposes it. A final vote on the tax plan is expected late Thursday night or Friday.

--This report was updated at 11:05 a.m.