Sen. Marco Rubio came out swinging Sunday at President-elect Donald Trump, criticizing his onetime adversary for considering Rex Tillerson as secretary of state because of his ties to Russia's President Vladimir Putin.
Rubio has already signaled his support of a congressional investigation into Russian involvement in the election, the Tampa Bay Times reported.
The newspaper on Sunday called Rubio's new tweet the "most overt criticism … has made as the new administration comes together."
Rubio became a frequent punching bag for Trump during the GOP primaries, when Trump dubbed him "little Marco."
After Trump's GOP nomination, however, the Florida Republican supported him.