Oklahoma senator James Lankford, a member of the intelligence committee, said on CNN Thursday that there's no doubt that Russia was behind the hacking of Democratic campaign officials.

"You heard DNI Clapper today say in those hearings that there is no doubt that Russia was behind the election interference. As you know, the president-elect continues to express doubts very publicly," CNN's Jim Sciutto said to Lankford. "Do you have any doubt that Russia perpetrated these attacks?"

"No," Lankford replied, "I don't have any doubt that Russia's been engaged in trying to interfere with our elections, just as they've done with other countries all around the world, all around their region. They've been very engaged in this. What I would dispute, and I've heard a lot of people comment on, is that Russia was trying to hack into our voting system and actually trying to change votes. I still hear that rumor, and it's been debunked over and over again." (A recent YouGov poll found that 52 percent of Democrats believe Russia tampered with vote tallies to get Trump elected.)

Lankford was then asked if he could "describe in general terms" the evidence that proved senior Russian leaders were behind the email hacking. "No, I can't," Lankford replied, saying that would reveal classified information.

Lankford's public break with Trump on the question of Russia's involvement in U.S. campaign email hacking is consistent with remarks of other congressional Republicans. "I think there's no question that Russia was involved," senator John Thune, the chair of the Senate GOP conference, said on CNN Thursday.

The GOP-controlled Senate demonstrated independence from Trump by holding its first hearing of the year on Russian campaign hacking, a subject about which the president-elect is very sensitive. The remarks of Lankford and Thune in particular are a promising sign that congressional Republicans aren't going to let Trump's popularity keep them from disagreeing with him publicly if they believe the facts warrant such a disagreement. In 2016, Trump carried freshman senator Lankford's Oklahoma by 36 points and won Thune's South Dakota by 30 points (while Thune himself won reelection by 44 points).

Although some Trump apologists like Sean Hannity and Sarah Palin have garnered attention for flip-flopping on the threat posed by Julian Assange, the founder of WikiLeaks, no elected Republicans seem to be joining them. On Wednesday morning, Trump publicly promoted the claim of Assange that Russia was not behind the hacking of campaign emails. House speaker Paul Ryan later called Assange a " sycophant for Russia," and Texas congressman Will Hurd, a former CIA officer, issued a statement blasting Assange as a not credible source who is endangering the lives of Americans and their allies. The next day, Trump tweeted: "The dishonest media likes saying that I am in Agreement with Julian Assange - wrong. I simply state what he states, it is for the people ... to make up their own minds as to the truth."