Sen. Marco Rubio, R-Fla., announced Monday that he will vote to confirm Rex Tillerson as secretary of state, after days of saying he hadn't decided whether to support the former Exxon Mobil CEO because of his business ties to Russia.

"I believe the president is entitled to significant deference when it comes to his choices for the cabinet," Rubio said in a Facebook post unveiling his decision. "Despite my reservations, I will support Mr. Tillerson's nomination in committee and in the full Senate."

Rubio's announcement of support for Tillerson comes after two other Republican Tillerson skeptics in the Senate, Sens. John McCain, R-Ariz., and Lindsey Graham, R-S.C., said they would vote for Tillerson as well.

Democrats mocked Rubio for giving into what Trump wants, given his opposition to Trump during the GOP primary. Democratic spokesman Zac Petkanas said Rubio's decision means he is "earning the nickname Trump gave him: Little Marco."