Hours before sitting down for lunch with Republican Senators at the U.S. Capitol, President Donald Trump renewed his feud with a retiring Sen. Bob Corker (R-TN), blasting Corker as a "lightweight," accusing him of standing in the way of tax reform, and repeating a string of debunked accusations against the chairman of the Senate Foreign Relations Committee, who wasted no time in firing right back at the President.
"Isn't it sad that lightweight Senator Bob Corker, who couldn't get re-elected in the Great State of Tennessee, will now fight Tax Cuts plus!" Mr. Trump tweeted, reigniting a Twitter feud from a few weeks ago.
The Twitter volleys by the President promised to make the GOP lunch into a somewhat uncomfortable gathering, just as the White House tries to rally Republicans behind a still-to-be-developed tax reform bill.
Corker, who has not been shy about criticizing the President for his diplomatic and military decisions - and use of Twitter - fired right back.
"The President has great difficulty with the truth on many issues," Corker told CNN in a live interview.
The visit by the President to the Capitol comes at an important time legislatively, as GOP lawmakers in the House and Senate are ready to cobble together the details of a tax reform package - as some want Mr. Trump to weigh in with details.
"What are his non-negotiables?" asked Sen. James Lankford (R-OK), who told reporters it's time for the President to deliver more specifics on what he likes - and doesn't like - when it comes to the fine print of tax reform.
"We've got big issues that are moving - those have to be resolved - and at least know where the President's priorities are," Lankford added in an interview just off the Senate floor.
On Monday, the President further unnerved Republicans when he proclaimed his opposition to any tax changes in the 401(k) program - it was exactly the kind of move that has worried GOP lawmakers, as they develop a tax bill.
While Republican lawmakers talked optimistically on Monday about unveiling the full details of a tax plan as early as next week, there were reports that the details weren't even finalized.
The first stop for tax reform will be the House Ways and Means Committee, chaired by Rep. Kevin Brady (R-TX), who told reporters on Monday that he's optimistic the Congress will be able to move quickly on the plan.
White House officials have repeatedly said that the average American family will see a benefit of around $4,000 from tax reform.
"If that's true it will be awesome, if it's not true, heads will roll," said Rep. Ted Yoho (R-FL).
"I just hope we can get it through," Yoho added.