"After many conversations over the past several days with individuals from both sides of the aisle across Tennessee and around the country," Corker said. "I have decided to support the tax reform package we will vote on next week."

And, after GOP leaders announced they'd expand the refundability of the child tax credit, Sen. Marco Rubio, a Republican from Florida, who'd threatened to vote against the tax package without a boost to the tax credit, announced his support.

Even with a few senators still on the fence, members are optimistic they'll have the bill on President Donald Trump's desk before Christmas, a remarkable position to be in given how elusive legislative victories have been for congressional Republicans all year.

"I'm confident at the end of the day, the Senate will approve this conference committee report," House Ways and Means Chairman Kevin Brady said Friday.

Rewriting the tax code was the kind of herculean lift many doubted Congress could pull off, especially after the Senate failed to repeal Obamacare last summer and again in the fall. But the pressure of delivering something -- anything -- weighed heavily on members, with some candidly confessing that donors had warned them to pass a bill or not bother asking for money next year when Republicans will be tasked with maintaining their majorities in both chambers.

"It's all about getting things done," said Rep. Mark Meadows, a Republican from North Carolina and the leader of the House Freedom Caucus. "If we don't get things done, we don't have to worry about the election in Alabama, we have to worry about our own elections back home."

But despite the massive victory, the vote still comes at a time when the Russia investigation -- both with the Justice Department's special counsel and with Congress' separate probes -- hangs over the GOP agenda and Trump continues to voice his frustration with it.

The congressional investigations into the matter are ongoing as well, meaning that Republican members of Congress -- happier to discuss their gains in dropping the corporate tax rate than Russia -- are still forced to answer for it.

But, Republicans will try to keep the focus on taxes this week. After all, it's the major overhaul they've been talking about for more than three decades.

"We just wanted to give our workers and everybody in the country a fair, level playing field ... that's what this President said since he started running for President," said Sen. David Perdue, a Republican from Georgia. "That's what I said four years ago when I started running for the United States Senate."