UPDATE | With Rubio onboard, GOP leaders finalize huge tax package

WASHINGTON (AP) — Republicans finalized the most sweeping overhaul of the nation's tax laws in three decades Friday, sweetening the child tax credit to placate a reluctant GOP senator as they pushed to muscle the bill through Congress next week and give President Donald Trump his first major legislative victory.

Sen. Marco Rubio, R-Fla., had been holding out for a bigger child tax credit for low-income families. After he got it, Rubio tweeted that the change is "a solid step toward broader reforms which are both Pro-Growth and Pro-Worker."

Rubio spokeswoman Olivia Perez-Cubas said that meant he'd vote yes. Rubio's support provided a major boost for Senate Republicans who are trying to hold together a razor-thin majority to pass the bill.

"I'm confident we'll have the votes," said Sen. Rob Portman of Ohio, one of the Republican negotiators on the bill.

Portman cast the bill as providing "the kind of middle-class tax relief that's desperately needed right now. People are looking at flat wages and higher expenses, and this will help."

Members of a House-Senate conference committee signed the final version of the legislation today, sending it to the House and Senate for final passage. They have been working to blend different versions passed by the two houses.

The tax package would double the basic per-child tax credit from $1,000 to $2,000. The bill makes a smaller amount available to families even if they owe no income tax. Rep. Kristi Noem, R-S.D., said Friday that that amount had been increased to $1,400.

Rubio had said he wanted the earlier $1,100 figure increased.

Low-income taxpayers would receive the money in the form of a tax refund, which is why it's called a "refundable" tax credit.

Senate Republicans passed their original tax bill by a vote of 51-49 – with Rubio's support. If they lost Rubio, they would have been one more defection away from defeat

Rubio's support came after a key faction of House Republicans came out in favor of the bill, increasing its chances. Members of the conservative House Freedom Caucus predicted the vast majority of their members would support the package.