The former presidential candidate could be a deciding vote on whether former ExxonMobil CEO Rex Tillerson will head the State Department.

Joshua Roberts / Reuters Senator Marco Rubio questions witnesses during a hearing on “Russia’s intelligence activities" on Capitol Hill January 10, 2017.

WASHINGTON — Florida GOP Sen. Marco Rubio, who has expressed concerns about President-elect Donald Trump's nominee for secretary of state Rex Tillerson and is a must-get vote for the nominee, wasted no time in grilling the former Exxon Mobil chief about his views on Russia Wednesday.

Rubio asked Tillerson about the Russian hacking of the Democratic National Committees emails during the 2016 election, sanctions against the country, his views on Russian President Vladimir Putin, and human rights abuses by foreign countries, expressing dissatisfaction repeatedly with the responses he was getting from Tillerson. Members of both parties have been particularly uncomfortable with the nominee's close ties to Putin. Rubio, whose support is crucial because Republicans have only a one-seat advantage on the committee, has been a vocal critic of Tillerson's relationship with the Russian president, and it wasn't clear if Trump's nominee had eased or aggravated the senator's concerns by the end of the hearing. "I'm prepared to do what's right," he told reporters after the hearing. "I'm not analyzing it from a partisan perspective...My view is that the president deserves wide latitude in his nominations. But the more important the position is, the less latitude they have."

Right from the start, @marcorubio is going in hard on Tillerson's views on Russia

During Wednesdays nine-hour hearing, Tillerson, who didn't use any notes throughout the day, acknowledged that the report on Russian hacking was "clearly troubling." But when asked if he believed Putin directed the hacking, Tillerson began dodging. "I'm not in a position to be able to make that determination," he told the Senate Foreign Relations Committee before admitting that it was a "fair assumption." Rubio then pushed Tillerson on whether he would advise Trump to keep the sanctions against Russia that the Obama administration ordered in response to the hacking. "The president-elect has indicated what's really required is a comprehensive assessment of cybersecurity policies," he responded. The former GOP presidential candidate continued his line of questioning, asking if Tillerson believed Putin to be a war criminal. "I would not use that term," he said, adding he hasn't had access to classified briefings to make that determination. Rubio also delved into the atrocities in Aleppo that have been widely reported, and then asked if Tillerson thought Putin was responsible for countless murders of dissidents. "I do not have sufficient information to make that claim," Tillerson responded.

.@marcorubio brings up Aleppo to try to get Tillerson to admit Putin has committed war crimes. Then says his respon… https://t.co/AqdeEf1s7i