Rubio accused Buttigieg of lying when he said Rubio’s letter was a call for deregulation. “He is an incompetent who is focused solely on his fantasies about his political future & needs to be fired,” Rubio tweeted.

“The facts don’t lie,” Buttigieg tweeted. “The 2021 letter you signed was obviously drafted by railroad industry lobbyists.”

“Now: will you vote to help us toughen rail safety accountability and fines, or not?” he continued.

The public sparring — a rare knives-out departure from Buttigieg’s usually collegial, Eagle Scout demeanor — highlights Buttigieg’s dual roles as Biden’s Transportation secretary and as a Democratic star with perceived presidential ambitions. Buttigieg presents a tempting target, considering shots at him potentially land a blow on Biden while also possibly tarring any future Buttigieg run for the White House.

Scott, meanwhile, challenged Buttigieg Tuesday over Twitter to go to the derailment site. “Hey, @SecretaryPete: the right time for folks in East Palestine is now,” Scott tweeted in response to a CNN story that quoted Buttigieg as saying he would go “when the time is right.”

“When leaders show up, things get done—enough with the excuses,” Scott tweeted. “Show up, do your job and stop playing politics with every crisis you find.”

Scott was continuing a Republican attack on Buttigieg for not going to the site soon enough after the accident.

Buttigieg responded Tuesday that he was trying to stay out of the way of investigators.

“During the initial response phase, I’ve followed the norm of staying out of the way of the independent NTSB,” Buttigieg tweeted Tuesday in response to Scott’s tweet. “Now that we’re into the policy phase, I’ll be visiting – and I need your help. Will you work with us to toughen accountability standards on freight railroads?”

Then he linked to DOT’s recent call for policy changes by railroads as well as legislative action by Congress, telling Scott, “If you’re serious, I’ll work with you on this.”