Flake and Corker — both of whom won't be seeking re-election next year — took their public feuds with Trump to the next level Tuesday even as they joined their GOP Senate colleagues for lunch with the president.
"Both of them are for tax reform," Portman said in a "Squawk Box" interview on Wednesday. "The notion I've heard this morning that they're somehow going to vote the other way because of their views about the president is crazy," the Ohio Republican continued. "They're going to do what's best for the people they represent."
Meanwhile, Trump baited Flake and Corker in a series of tweets Wednesday morning.
Instead of focusing on the president's tweets, lawmakers need to work toward cutting taxes and lowering health-care costs, said Portman, who had been discussed as a possible vice presidential pick for Trump during the campaign. "We shouldn't allow Twitter to distract us from the work we're supposed to be doing."
"You have to work with the president," he added, saying he even worked with Democrat Barack Obama when he was president. "Our job is to put our head down and start legislating."
Portman said he's not a rubber stamp for Trump, saying he does speak up when he disagrees with the president.