Herb Jackson and Deirdre Shesgreen

USA TODAY

WASHINGTON — A sweeping overhaul of the tax code gained significant momentum on Friday as GOP negotiators in the House and Senate signed off on a final agreement that sweetened a key tax credit and wavering GOP senators announced their support.

Raising the child tax credit won over at least one GOP holdout, Sen. Marco Rubio, who said on Friday he would be a yes after threatening to scuttle the deal only 24 hours earlier.

And in a major reversal, Sen. Bob Corker of Tennessee, said Friday he would support the bill, despite voting against a similar bill earlier this month because of concerns it would add to the national debt.

“This bill is far from perfect, and left to my own accord, we would have reached bipartisan consensus on legislation that avoided any chance of adding to the deficit,” Corker said in a statement Friday. He said he decided to support the bill now because the country is “better off with it” than without it.

Those two new "yes" votes put the bill on solid ground for final passage next week. Supporters of the bill exuded confidence on Friday that they would have the votes when the final tallies are called. But there are at least a few wildcards left in the GOP deck: along with several senators who remain undecided on the bill, two have missed votes this week because of medical issues.

Republicans hold a narrow 52-48 majority in the Senate, so they can only lose two GOP votes and still pass a bill with Vice President Mike Pence serving as a tiebreaker. All the Senate’s Democrats are expected to oppose the measure.

The tax bill passed its final procedural hurdle Friday just after noon when the chairman of the Ways and Means Committee, Rep. Kevin Brady of Texas, said Republicans had signed off on the report of a House-Senate conference committee and would release the text Friday night.

"I’m confident at the end of the day the Senate will approve this conference committee report because no one should be defending the status quo, the horrible tax code Americans have had to live with for too long," Brady said.

Friday's final deal included a last-minute provision added to win over two GOP hold-outs: Sens. Marco Rubio of Florida and Mike Lee of Utah. Those two lawmakers sought a boost in the child tax credit, so GOP negotiators agreed to plump it up for low-income families.

The current tax code provides a credit of up to $1,000 per child to parents, but that break phases out for those with incomes above $110,000.

Under the agreement reached on Friday, the credit would increase to $2,000 per child, and the income cutoff would go to $500,000. In addition, $1,400 of the credit would be refundable, meaning that parents could get that amount from the government even if their wages were so low they did not owe income tax.

That's $300 more than GOP negotiators agreed to earlier this week — a change made after Rubio and Lee threatened to torpedo the measure without a more generous credit.

The change was enough to get Rubio's support. He said on Twitter that making 70% of the total credit refundable "is a solid step toward broader reforms which are both pro-growth and pro-worker. But there is still much more to do in the months and years to come."

He thanked Lee, as well as Sen. Tim Scott of South Carolina and Ivanka Trump, the president's daughter and adviser who also advocated for the credit.

Lee said in a statement he was leaning in favor of the bill Friday, though still reviewing the details.

“I look forward to reading the full text of the bill and, hopefully, supporting it,” Lee said.

Asked about Rubio and Lee as he left the White House for a speech Friday, President Trump was confident.

“They want to see it done,” Trump said. “I know how they feel. These are great people and they want to see it done, and they want to see it done properly.”

Two other Republican senators remained undecided: Jeff Flake of Arizona and Susan Collins of Maine — with each weighing different concerns.

Adding to the uncertainty: Sen. John McCain, R-Ariz., is undergoing treatment for brain cancer and was hospitalized this week at Walter Reed Medical Center. And Sen. Thad Cochran, R-Miss., had outpatient surgery on Monday to remove a lesion on his nose, said his spokesman Chris Gallegos, and “the procedure was more extensive than expected.”

Sen. Rob Portman, an Ohio Republican who helped negotiate the final deal, said he was confident Republicans would have the votes for Senate passage. He said he expected both McCain and Cochran to be in Washington next week despite their medical problems.

Asked if Republicans could pass the bill without McCain’s vote, Portman said: “I don’t want to go there, because I think John McCain will be here.”

“He’s having a tough time, but I’m told that he will be here next week and voting,” Portman said. “More importantly we all wish him the best of health.”

Contributing: Eliza Collins and Ledyard King

Read more:

Changes coming in the tax bill to be released Friday, and some of the reasons for them

Why is President Trump still talking about a tax bill instead of signing one?

Trump says Republicans are just 'days away' from tax cut bill – maybe