WASHINGTON — As crunch time emerged in the GOP’s push to pass a $1.5 trillion tax cut, wavering Republican senators inevitably made the trip from the Senate floor to an office tucked just a few paces away.

They entered and walked past a painting of Alamo legend William Barrett Travis. Past the crackling flames of one of the Capitol’s few working fireplaces. Past a fake Christmas tree, at least in the latter stages of the proceedings, that’s festooned with lights.

And then they aired their grievances to Texas Sen. John Cornyn, the Senate’s No. 2 Republican.

“There was always two or three things with each of these individuals,” he told The Dallas Morning News in that same office that’s home to his whip operation. “The implied threat that they would withhold their vote for the final product was enough to require a negotiation.

“And that’s basically how legislation gets written.”