Sen. Marco Rubio expressed concern about Donald Trump's pick for secretary of state Rex Tillerson, but said he'd ultimately vote for him. | Getty Rubio to back Tillerson, effectively ensuring confirmation

Sen. Marco Rubio put aside serious reservations about Rex Tillerson and announced Monday he'll back the former ExxonMobil chief for secretary of state, effectively clinching his confirmation.

The support of the Florida Republican means Tillerson will clear a Monday evening in the Senate Foreign Relations Committee instead of facing an embarrassing "unfavorable" verdict by the panel. Rubio's decision likely foreshadows unanimous GOP support for Tillerson, who had made some Republicans nervous about his closeness to Russian President Vladimir Putin and reluctance to criticize Putin's actions during his confirmation hearing.


Even in his Facebook post announcing his position, Rubio highlighted Tillerson's ambiguity when asked directly about whether Putin is a "war criminal" or whether authoritarian governments are human rights violators. But ultimately Rubio said it would not be productive to stand in the way of Tillerson and tag him with bipartisan opposition.

"I remain concerned that in the years to come, our country will not give the defense of democracy and human rights the priority they deserve, and will pursue a foreign policy that too often sets aside our values and our historic alliances in pursuit of flawed geopolitical deals," Rubio said. “Given the uncertainty that exists both at home and abroad about the direction of our foreign policy, it would be against our national interests to have this confirmation unnecessarily delayed or embroiled in controversy,”

The Trump administration exerted a full-court press on Rubio in recent days. Rubio met with Tillerson last week and said afterward that Tillerson had addressed "some" of his concerns. Republican senators predicted that Rubio would ultimately vote for Tillerson, arguing it made no sense for the Florida senator to invite retribution from Trump just days into a new administration.

In his lengthy statement, Rubio moved to rebut forthcoming criticisms of him as grandstanding in his public skepticism about Tillerson. The Flordia senator vowed to take a hard line against lower-level nominations that the Senate Foreign Relations Committee will take up.

"Upcoming appointments to critical posts in the Department of State are not entitled to and will not receive from me the same level of deference I have given this nomination," Rubio said.

Still, the dramatic posturing by Rubio, combined with his ultimate deference to Trump, gave new fuel to Democratic critics who have long mocked him for calling Trump a "con man" last year, then endorsing him for president and standing by him through months of controversy.

“By ignoring his serious reservations about Tillerson’s connections to Vladimir Putin, Marco Rubio is not only rolling over for Donald Trump, he’s earning the nickname Trump gave him: Little Marco," said DNC Senior Adviser Zac Petkanas.

Tillerson's nomination represented the first major confrontation between the Senate GOP and Trump, but ultimately the hawkish opposition to Tillerson dissolved as his confirmation vote drew near. First Sen. John McCain (R-Ariz.) said Sunday he will support Tillerson, then Sen. Lindsey Graham (R-S.C.) fell in line.

The support of those two senators effectively ensured TIllerson would be confirmed — and gave Rubio space to oppose Tillerson without tanking the nomination. But ultimately Rubio went in the opposite direction.

"Mr. Tillerson implied that speaking out on human rights would hinder his ability to do his job as the nation’s chief diplomat," Rubio said on Monday. "But in making my decision on his nomination I must balance these concerns with his extensive experience and success in international commerce, and my belief that the president is entitled to significant deference when it comes to his choices for the cabinet."