Marco Rubio rescued Donald Trump's nominee for for secretary of state on Monday morning.

The Republican senator said he would support Rex Tillerson when his confirmation comes before the Senate Foreign Relations committee today, despite significant reservations over the former oil baron's personal relationship with Russian strongman Vladimir Putin.

'I believe the president is entitled to significant deference when it comes to his choices for the cabinet,' Rubio said.

Tillerson's appointment to the post hinged on Rubio voting yea. The full Senate must also approve him, but Rubio and two other Republicans who could have derailed Tillerson said they would vote along party lines, all but assuring his confirmation.

Decision time: Rex Tillerson, the former Exxon CEO who attended President Trump's inauguration with his wife Renda, will receive a vote from the Senate Foreign Relations Committee today

The decision was in the hands of Marco Rubio. Rubio said this morning that he will vote yea

Lukewarm backing: John McCain and Lindsey Graham both offered endorsements of Tillerson, suggesting he would be approved if Rubio allowed his nomination to come before the full Senate

Rubio, whom Trump defeated for the GOP presidential nomination last year, clashed with Tillerson at a committee hearing earlier this month.

The Florida senator bridled at Tillerson's refusal to label Russian President Vladimir Putin a 'war criminal' or condemn human rights violations in Saudi Arabia and the Philippines in strong enough terms. He chided Tillerson over the need for 'moral clarity.'

'Despite his extensive experience in Russia and his personal relationship with many of its leaders, he claimed he did not have sufficient information to determine whether Putin and his cronies were responsible for ordering the murder of countless dissidents, journalists, and political opponent,' the Republican senator said in a statement Monday.

Rubio said he continues to have concerns about Tillerson's position on sanctions.

The millionaire said at a hearing that he would only support punishing actions if they met the 'impossible condition that they not affect U.S. businesses operating in Russia.

'While he stated that the "status quo"should be maintained for now on sanctions put in place following Putin’s illegal taking of Crimea, he was unwilling to firmly commit to maintaining them,' Rubio said.

The Republican senator said he was, however, 'encouraged' by Tillerson's assertion that Russia hacked the emails of Democrats as the intelligence community has claimed and his declaration that the Russian invasion of Crimea was illegitimate.

He was ultimately convinced to vote for Tillerson, who he described as qualified and patriotic, based on his belief that it 'would be against our national interests to have this confirmation unnecessarily delayed or embroiled in controversy.'

' 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 in a lengthy Facebook post.

'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.'

His vote was effectively the deciding one in the case of Tillerson's nomination.

A refusal by Rubio would have presented the Trump administration with its first clash with the Senate and force them to find a new nominee.

Decision time: The top Democrat on the Senate Foreign Relations Committe, Ben Cardin, says he will not vote for Rex Tillerson, suggesting that all Democrats on the committee will follow him. That made Rubio the deciding vote

The scenario became less likely on Sunday after two influential Republican senators — John McCain of Arizona and Lindsey Graham of South Carolina — offered tepid endorsements of the former Exxon Mobil chief.

The top Democrat on the Senate Foreign Relations Committee had said he could not support Trump's nominee for secretary of state, and other Democrats on the committee are expected to follow him.

Sen. Ben Cardin of Maryland said in a statement ahead of the vote that Tillerson's business orientation and confirmation hearing answers could compromise his ability to forcefully promote U.S. values and ideals.

Specifically, Cardin said he based his opposition on Tillerson's unwillingness to call Russia and Syria's atrocities 'war crimes,' or to describe Philippine President Rodrigo Duterte's extrajudicial killings as gross human rights violations.