Going into Wednesday's hearing for President-elect Donald Trump's secretary of state nominee, Rex Tillerson, all eyes were on Sen. Marco Rubio (R-Fla.), who could choose whether to give deference to Trump's pick — or try to tear him apart.

In the opening hour of the two-day hearing, Rubio went on the attack. [Notably, Senate Foreign Relations Committee Chairman Bob Corker (R-Tenn.) let him go on that attack before many other senators had a chance to speak, and before Trump's news conference was going to suck up all the political oxygen.]

No matter when it happened, Rubio's bull-dog approach could spell trouble for Tillerson's nomination and signal a larger rift within the Republican Party about whether to work with Trump on sensitive issues like Russia.

Rubio signaled that he has no intention of deferring to Trump on the issue of Russia. He came out in full bulldog mode about Tillerson's economic and personal ties to Russia and its president, Vladimir Putin.

UPDATE: Senate Democrats are taking full advantage to try to exploit this moment. Here is Senate Minority Leader Chuck Schumer (D-N.Y.) on the Senate floor on Wednesday:

The Florida senator started by asking Tillerson whether he acknowledged the finding from U.S. intelligence agencies that the president-elect has not:

1) Does he believe Russia tried to interfere in the U.S. election? (Tillerson hedged. "[The newly declassified intelligence] report is clearly troubling.")

2) Does he think Russian President Vladimir Putin is behind those actions? (After some pressing, Tillerson said, "That's a fair assessment.")

3) Does he essentially agree with the Obama administration about slapping sanctions on Russian individuals believed to have played a role in the hacking. (Tillerson would not commit to advising Trump to keep those sanctions: "I would want to examine it.")

Then Rubio, clearly out for blood at this point, dropped this on Tillerson: "Is Vladimir Putin a war criminal?"

Tillerson: "I would not use that term."

Rubio was not happy with that answer. "Let me describe a situation in Aleppo and perhaps that will help you reach that conclusion," he said, going on to detail how Russia has targeted schools and markets in war-torn Syria, "resulting in the death of thousands of civilians."

"It should not be hard to say that Vladimir Putin is a war criminal," Rubio continued, "and I find it discouraging your inability to cite that, which I think is globally accepted."

His time running out for questions, Rubio lobbed one more attack at Tillerson by asking him whether he believes Putin is behind "the murder of countless political opponents."

Tillerson hedged on that too. He said he'd "want to have more information" before he assigned blame. "People who speak up for freedom in regimes that are oppressive are often a threat," he allowed.

Rubio's time for questions had run out, but he had broadcast his message loud and clear: He has no intention of playing nice with Trump's pick for secretary of state and, perhaps, with Trump himself when the two disagree on foreign policy.

Rubio's performance Wednesday was also a batman signal of sorts to hawkish Republicans like Sens. John McCain (Ariz.) and Lindsey O. Graham (S.C.) that he's inclined to join their team. McCain and Graham have expressed deep concern about Russia's influence in the U.S. election and Trump's inability to fully acknowledge it, going so far as to request a special investigative committee to look into what Russia did, while Trump has signaled he just wants the whole world to forget about it and move on.

As The Post's dean of congressional political coverage, Paul Kane, explained smartly in his column Tuesday, a  growing coalition of hawkish Senate Republicans could present a problem for Trump::

A forceful attack on Trump’s seemingly friendly stance toward Russia would win credit with many traditional GOP foreign policy experts, but it could renew the personal battles with the president-elect that played out during the Republican nominating contest.

Several GOP senators on the sidelines who have concerns about Tillerson told Kane they'd be watching Rubio on Wednesday to see which team he's on and whether they should join too. Rubio, so far, is leaving little doubt he's with the hawks.

See photos from the confirmation hearings of Trump’s Cabinet nominees

WASHINGTON, DC - JANUARY 12: Ben Carson, Secretary of HUD nominee, pauses while answering questions from the Senate Housing Committee during confirmation hearings at the Dirksen Senate Office Building on January 12, 2017 in Washington, D.C. (Ricky Carioti/The Washington Post)