The lineup at Thursday's committee hearing included:

Director of National Intelligence James R. Clapper Jr.

Adm. Mike Rogers, commander of the U.S. Cyber Command and director of the National Security Agency

Defense Undersecretary for Intelligence Marcel J. Lettre II

Here are the big takeaways from the hearing. (For more detailed coverage, be sure to read Ellen Nakashima and Karoun Demirjian's article in The Washington Post.)

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1. Intelligence officials think Russians definitely meddled in the U.S. campaign

Russians hacked into party databases and candidate emails, and tried to spread propaganda and fake news. Basically, they tried everything they could to meddle in the presidential campaign, intelligence officials said Thursday. (The CIA and the FBI agree that Russia wanted to help Trump win.)

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Why did they do all this? We have to take a 30,000-foot view to answer that question.

“The Russians are bent on establishing a presence in the Western hemisphere” for a variety of reasons, Clapper said. He said they want to gain military allies, sell equipment, set up air bases and, crucially, set up intelligence-gathering facilities.

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And intelligence officials think Russia is getting more and more aggressive in trying to extend its reach to our side of the world; its hacking into Democratic emails is Exhibit A.

2. Russia's leaders authorized some of the hacking

The three intelligence officers released a statement before the hearing. One key line in it read that only “Russia's senior-most officials” could have authorized the hacking of the Democratic Party's emails.

The leaks arguably had an impact on Democrats at a critical moment in their campaign: You'll recall that some of those emails were leaked on the eve of the Democratic National Convention in the summer and resulted in the resignation of Rep. Debbie Wasserman Schultz (D-Fla.) as chairman of the Democratic National Committee.

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This assertion that Russia's top leaders signed off on this directly flies in the face of Trump's insistence on repeatedly giving Russian President Vladimir Putin the benefit of the doubt. Shortly before the new year, Trump praised Putin for not retaliating to President Obama's sanctions on Russia for the hacking.

Most recently, Trump promoted a theory by WikiLeaks founder Julian Assange that Russia had nothing to do with the hack — taking him at his word, despite the findings of his own intelligence community.

Clapper dismissed that idea outright on Thursday, and The Post's nonpartisan fact-checking team said Assange's claims that Russia wasn't involved are a “distortion of the facts.”

UPDATE: Thursday afternoon, Trump appeared to reverse his earlier tweet aligning himself with Assange:

3. There's no way to know the electoral effect of Russia's supposed meddling

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No one alleging Russian hacking has insinuated that it propelled Trump to victory, and intelligence officials repeated that Thursday.

Clapper: “We have no way of gauging the impact, certainly the intelligence community can’t gauge the impact, it had on choices the electorate made.”

Senate Republicans tried to make that clear as well:

Of course, the fact that those lines could be drawn between Russia's hacking and Trump's win seems to be Trump's main beef with all this. After all, he won three key states — Michigan, Pennsylvania and Wisconsin — by less than 1 percent. Absent those very narrow wins, we'd probably have spent the past two months talking about President-elect Hillary Clinton's massive popular vote victory. The idea that WikiLeaks revelations could have shifted even a fraction of votes in those key states — and that Russia could have been behind those revelations — is obviously a very, very sensitive one for the president-elect.

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4. Intelligence leaders feel the need to defend themselves from attacks like Trump's

The quote that will probably make the most headlines from this hearing comes from Clapper, who said that skepticism of intelligence is healthy (“the intelligence community is not perfect”) but that “I think there is a difference between skepticism and disparagement.”

He went on to say: “I don’t think the intelligence community gets the credit it’s due for what it does day in and day out to keep this nation secure.”

Clapper, nor anyone else testifying at Thursday's hearing, didn't directly point fingers at the president elect. But Trump was definitely the elephant in the room.

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5. Some Senate Republicans are ready to get tough on Russia, regardless of whether Trump is on board

It's probably not a coincidence that this hearing was held just two days after the new Congress was sworn in.

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McCain has been vocal about his desire to thoroughly investigate Russian efforts to affect U.S. politics since The Post reported that the CIA thinks Russia tried to sway the election for Trump. Crucially, Senate Majority Leader Mitch McConnell (R-Ky.) has given his approval to some of the investigations.

Another vocal hawk, Sen. Lindsey O. Graham (R-S.C.), said in the hearing that he wants to “throw rocks” at Russia.

McCain, along with Senate Democrats, also wants to up the ante by putting together a special investigative committee, not unlike House Republicans' two-year investigation of the 2012 terrorist attacks in Benghazi, Libya. It remains to be seen whether GOP leaders will sign off on a full-blown separate investigation. But in the meantime, expect plenty of day-long hearings like what we just saw Thursday.

6. We'll know more about what the intelligence community thinks next week