First Read is your briefing from Meet the Press and the NBC Political Unit on the day's most important political stories and why they matter.

WASHINGTON — Over the past year, we’ve witnessed prominent Republicans — who’ve been critical of President Trump and his volatile behavior — still stand behind the president or his policies.

Retiring Sen. Jeff Flake, R-Ariz., who denounced Trump on the Senate floor back in October ("When the next generation asks us: 'Why didn't you do something? Why didn't you speak up?' What are we going to say?"), has consistently voted for Trump’s policies and nominees.

Retiring Sen. Bob Corker, R-Tenn. – who also blasted Trump last fall ("His governing model is to divide and to attempt to bully and to use untruths”) — still voted for Trump’s tax legislation.

And Sen. Lindsey Graham, R-S.C., who said Trump was “crazy,” “unifit” and “a kook” during the 2016 GOP presidential primaries, has emerged as a key Trump ally.

On “Meet the Press” yesterday, Graham explained why he still sticks up for Trump: 1) because Trump is president, and 2) because Trump can help him with his policy goals.

CHUCK TODD: I've got to ask you something. The president sort of joked with you the other day and he said, "Boy, Lindsey used to be a great enemy of mine, and now he's a great friend of mine." What's changed? A lot of, a lot of your friends have been asking me that, going, "Hey, ask the senator why he's suddenly cozying up to President Trump." What would you say to them?SENATOR LINDSEY GRAHAM: Because he's president of the United States, he's going to make a decision about immigration, I've been working on for a decade. He's president of the United States, going to make a decision about North Korea, which is one of the biggest threats to the world at large. He's going to decide whether or not to stay in the Iranian agreement. I've enjoyed his company. He beat me like a dog. I've said everything I know to say about him. I, I used every adjective on the planet. I lost, he won. And I feel an obligation to help him where I can. I've enjoyed working with him. I don't think he's crazy. I think he's had a very successful 2017. And I want to help him where I can. And we should all want him to be successful. He's got a lot on his plate.

In other words, if Graham still denounced as a “kook” and “unfit,” he’d be unable to influence the president on immigration and North Korea. And Graham sees it as an obligation to help Trump succeed.

Bottom line: The congressional GOP’s relationship with Trump isn’t going to change until people back up their words with action. And everything we have learned about the Trump presidency over the past week — the “Fire and Fury” book, Trump’s relatively empty schedule, his reaction to questions about his stability — is troubling. And remember, the job hasn’t really gotten hard yet; there has been no international crisis in Year One.

Lindsey Graham on the Russia probe: “Bob Mueller is doing a great job”

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Also in his interview on “Meet the Press” yesterday, Graham said he stood behind special counsel Robert Mueller’s Russia probe. “All I can say is that it's not a hoax. The Russians stole the emails. They did interfere in our elections. We now know that Trump Junior met with the Russians in Trump Tower and that Bob Mueller is doing a great job. He's the right guy at the right time. He needs to be allowed to do his job.”

But he also said there needs to be a second special counsel to investigate potential wrongdoing at the Justice Department and FBI. “There's a bunch of stuff about the Department of Justice, how they conducted themselves, that need to be looked at just as much as Trump needs to be looked at.”

“A very stable genius”

Additionally on “Meet” yesterday, the author of the new “Fire and Fury” book on the Trump White House said that concern of Trump’s stability has become so great that the 25th Amendment has become a frequent topic inside 1600 Pennsylvania Avenue.

Michael Wolff “said White House staffers he talked to would say things like ‘we're not at a 25th Amendment level yet.’ Others, he said, called Trump's behaviors ‘a little 25th Amendment,’” per NBC’s Kailani Koenig. The 25th Amendment would allow the president’s cabinet to remove him from office.

Responding to those kinds of allegations, Trump took to Twitter over the weekend. “Actually, throughout my life, my two greatest assets have been mental stability and being, like, really smart,” adding: “I went from VERY successful businessman, to top T.V. Star to President of the United States (on my first try). I think that would qualify as not smart, but genius....and a very stable genius at that!"

Trump also said this at Camp David Saturday: “I went to the best colleges for college. I went to a — I had a situation where I was a very excellent student. Came out and made billions and billions of dollars. Became one of the top businesspeople.”

Bannon’s non-apology apology

On Sunday, according to NBC’s Hallie Jackson, Kelly O’Donnell and Kristen Welker, Steve Bannon released a statement backtracking from calling that June 2016 Trump Tower meeting between Donald Trump Jr./Paul Manafort/Jared Kushner and the Russians as “treasonous” and “unpatriotic.” But it wasn’t a full backtrack. Here’s the statement:

Donald Trump, Jr. is both a patriot and a good man. He has been relentless in his advocacy for his father and the agenda that has helped turn our country around.My support is also unwavering for the president and his agenda — as I have shown daily in my national radio broadcasts, on the pages of Breitbart News and in speeches and appearances from Tokyo and Hong Kong to Arizona and Alabama…My comments about the meeting with Russian nationals came from my life experiences as a Naval officer stationed aboard a destroyer whose main mission was to hunt Soviet submarines to my time at the Pentagon during the Reagan years, when our focus was the defeat of 'the evil empire,’ and to making films about Reagan's war against the Soviets and Hillary Clinton's involvement in selling uranium to them.My comments were aimed at Paul Manafort, a seasoned campaign professional with experience and knowledge of how the Russians operate. He should have known they are duplicitous, cunning and not our friends. To reiterate, those comments were not aimed at Don Jr.Everything I have to say about the ridiculous nature of the Russian 'collusion' investigation I said on my 60 Minutes interview. There was no collusion and the investigation is a witch hunt.I regret that my delay in responding to the inaccurate reporting regarding Don Jr. has diverted attention from the president's historical accomplishments in the first year of his presidency.

As NBC’s Jonathan Allen decodes the statement, Bannon doesn’t deny he said the meeting was treasonous and unpatriotic; he admits he can’t afford to alienate Donald Trump Jr.; he stresses that the Russians are a potential threat; and he doesn’t mention Jared Kushner AT ALL.

In First Read last Friday, we observed how Trump didn’t hold a single public event in first workweek back from the Christmas/New Year’s holiday. And yesterday, Axios’ Jonathan Swan reported on Trump’s shrinking schedule.

“President Trump is starting his official day much later than he did in the early days of his presidency, often around 11am, and holding far fewer meetings, according to copies of his private schedule shown to Axios,” Swan writes. “This is largely to meet Trump’s demands for more ‘Executive Time,’ which almost always means TV and Twitter time alone in the residence, officials tell us.”

By the way, here’s Trump’s schedule today: He speaks at the American Farm Bureau Federation’s annual convention in Nashville, Tenn., at 4:10 pm ET, and then he attends the NCAA national championship football game in Atlanta.

NBC scoop: Talks are underway about Trump’s interview with Mueller

NBC’s Kristen Welker, Carol Lee, Julia Ainsley and Hallie Jackson: “Anticipating that Special Counsel Robert Mueller will ask to interview President Donald Trump, the president’s legal team is discussing a range of potential options for the format, including written responses to questions in lieu of a formal sit-down, according to three people familiar with the matter."

More: “Trump’s legal team is seeking clarification on whether the president would be interviewed directly by Mueller, as well as the legal standard for when a president can be interviewed, the location of a possible interview, the topics and the duration. But the president’s team is also seeking potential compromises that could avoid an interview altogether, two of those interviewed told NBC News.”