Appearing on CNBC's "Squawk Box," Rubio was asked to respond in real time as President Donald Trump used Twitter to attack Corker and accuse the retiring senator of "fighting tax cuts." Trump also predicted that Corker would lose an election for dog catcher, were he to run.
"I think [Corker] will be" on board for a final vote, Rubio said. "All that other stuff is interesting to cover, but it has nothing to do with the reason why we're doing this," he said. "So let's stay focused on the taxes, and we'll leave the drama to other people."
As the deadline nears for producing a tax reform bill, Republicans are struggling to find enough new sources of revenue in the tax code to offset part of the nearly $4 billion cost of massive tax cuts for corporations and individuals. Their efforts have been hampered by a series of promises the president has made publicly, including vows to not touch popular programs and deductions.
Corker has emerged in recent weeks as one of the more vocal opponents of creating massive new deficits on the scale that some analysts are predicting.
"It's easy to talk about cutting people's rates and doing the things that benefit people," Corker said Tuesday morning on ABC. "But if you start taking things off the table before you get started, you make that very difficult. And what I hope is going to happen is the president will leave this effort to the tax writing committees."
Moments later, the president lashed out.
A few hours after his tweets, Trump was scheduled to attend a weekly lunch with Republican senators.