Sen. Bob Corker, R-Tenn., the only Republican to vote against the Senate's version of the GOP tax bill, announced Friday that he has changed his mind and will vote yes.
"After many conversations over the past several days with individuals from both sides of the aisle across Tennessee and around the country—including business owners, farmers, chambers of commerce and economic development leaders—I have decided to support the tax reform package we will vote on next week," Corker said in a statement Friday afternoon.
"This bill is far from perfect," he said, "but after great thought and consideration, I believe that this once-in-a-generation opportunity to make U.S. businesses domestically more productive and internationally more competitive is one we should not miss."
With Corker's support, the tax reform bill has crossed what many viewed as a final hurdle, virtually assuring that the legislation will eventually become law.
Corker's announcement came less than an hour after Sen. Marco Rubio said he would support the bill as well, after the GOP made changes to win his vote. The Florida Republican's backing also gave a major boost to the GOP's chances of approving the plan next week.
After arriving at his final decision, Corker phoned President Donald Trump, the White House said, adding that the president "greatly appreciated" the senator's support. Corker is one of Trump's most vocal critics in the Senate, and it was unclear if the president and Corker had actually spoken.
On Friday, Rep. Kristi Noem, R-S.D., told reporters that the GOP would increase the refundable part of the proposed $2,000 credit to $1,400 from $1,100. Doing so effectively expands it to more families.
On Thursday, Rubio said, "I won't support the bill" unless GOP leaders expand the child tax credit, increasing the portion of the credit that is refundable. Sen. Mike Lee, R-Utah, who has not yet committed to supporting the bill, also sought more tax relief for working families.
A Lee spokesman did not immediately respond to a request to comment on whether he will support the bill after the child tax credit changes.
Rubio's possible opposition had thrown more uncertainty into the GOP's push to pass a bill overhauling the U.S. tax system by next week. Sen. Bob Corker, R-Tenn., opposed the Senate version of the bill.
If Rubio had voted against the bill, as well, only one more Republican vote of opposition would have killed it.
The GOP released the final version of the bill on Friday.
Republicans are optimistic they have the votes to pass their plan next week, despite challenges in the Senate.
"I'm confident at the end of the day the Senate will approve this conference committee report," Brady told reporters Friday.
Sen. Susan Collins, R-Me., appeared to move closer toward supporting the GOP's final version of the bill. Collins touted the inclusion of three amendments that she backed as a "victory for middle-income Americans."
Those provisions include a state and local tax deduction of up to $10,000; a medical expense deduction; and the reversal of a proposal to eliminate catch-up contributions for retirement accounts for church, charity, school and public employees.
Though Collins voted for the Senate version of the GOP's tax plan, she has not yet decided whether to support the final version.
GOP Sens. John McCain of Arizona and Thad Cochran of Mississippi have missed votes this week due to health reasons, though Senate leaders have said they will be available to help push the tax bill through next week.
— CNBC's Ylan Mui contributed to this report