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 — Republicans already have plenty of disadvantages heading into the 2018 midterms — history (the party controlling the White House typically fares poorly), President Trump’s approval rating (which sits between 35 and 40 percent) and the start of some key retirements (like what we saw last week).

And now you can potentially add another disadvantage for the GOP: Former White House chief strategist Steve Bannon, who’s now back at Breitbart News, is plotting primaries against as many as four Senate Republican incumbents, per Politico.

The four are Nevada’s Dean Heller, Arizona’s Jeff Flake, Tennessee’s Bob Corker and Mississippi’s Roger Wicker. (Corker tells CNN that he’s mulling whether he’ll seek re-election.)

“Bannon has begun holding private meetings with insurgent challengers, vowing his support. He’s coordinating with conservative mega-donor Robert Mercer, who is prepared to pour millions of dollars into attacks on GOP incumbents,” Politico’s Alex Isenstadt writes.

“Bannon has also installed a confidant at an outside group that is expected to target Republican lawmakers and push the Trump agenda.”

Beyond dividing the party and creating more distrust between the White House and Senate Republican leaders, the problem with this Bannon/Breitbart campaign is that the Senate battlefield is perhaps the GOP’s top strength this midterm cycle, with Republicans having just nine seats to defend versus 25 for the Democrats. And that strength could now be at risk.

As the Cook Political Report’s Jennifer Duffy observes, “GOP primaries against incumbents are the only way Democrats can win a majority” — with Democrats needing to pick up three seats to win back the Senate.

In 2016, Bannon proved his effectiveness in being able to tear apart Hillary Clinton and Democrats. In 2018, will he tear apart the Senate GOP?

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Bannon: Yes, Trump firing Comey was the biggest mistake in modern political history

Speaking of Bannon, he pretty much admitted to CBS’ “60 Minutes” that Trump firing former FBI Director James Comey was the biggest mistake in modern political history. Strikingly, this exchange wasn’t included in CBS’ broadcast of the Bannon interview:

CHARLIE ROSE: It has been reported that Jared Kushner was in favor of firing James Comey. Is that correct?STEVE BANNON: I have — you guys have to ... find that out either through the media or through investigation. I don't know.CHARLIE ROSE: It is also true, many say, and you're a smart guy, that if James Comey had not been fired we would not have the Mueller investigation.STEVE BANNON: True. I don't think there's any—STEVE BANNON: —I don't think there's any doubt that if James Comey had not been fired, we would not have a special counsel, yes.

[snip]

CHARLIE ROSE: Do you believe that Mr. Mueller should be fired?STEVE BANNON: No, I do not.

[snip]

CHARLIE ROSE: Someone said to me that you described the firing of James Comey, you're a student of history, as the biggest mistake in political history.STEVE BANNON That would be probably — that probably would be too bombastic even for me, but maybe modern political history.CHARLIE ROSE: So the firing of James Comey was the biggest mistake in modern political history.STEVE BANNON: I think — if you're saying that that's associated with me, then I'll — I'll leave it at that.

Trump’s voter fraud panel is headed to New Hampshire. Here’s why it’s controversial

NBC's Dartunorro Clark writes that President Trump's vote-fraud panel is slated to conducted a public hearing Tuesday in New Hampshire — which just happens to be a state Trump lost in 2016, and where he alleged voter fraud took place (without any evidence to back it up).

Clark adds that this meeting comes after the panel's vice chair "amplified the president's baseless claims in an op-ed that illegal voting had possibly swayed the election in the state. 'It has long been reported, anecdotally, that out-of-staters take advantage of New Hampshire’s same-day registration and head to the Granite State to cast fraudulent votes,' Kris Kobach, the Kansas secretary of state, wrote on Breitbart last week."

"He added that it is 'possible that New Hampshire’s four Electoral College votes were swung to Hillary Clinton through illegal voting by nonresidents.'"

As it turns out: "In the op-ed, Kobach, the commission's vice-chair, cited driver's license and voter registration data released last week at the request of New Hampshire's Republican House Speaker, Shawn Jasper. The data showed over 6,500 people who voted in last year’s election had out-of-state licenses, which experts said is no evidence of voter fraud. State law allows people with non-New Hampshire driver's licenses to live in the state and vote legally" — like students and members of the U.S. military.

Katy Tur: Don’t ever count out Donald Trump

Our colleague Katy Tur, who has a new book out entitled “Unbelievable: My Front-Row Seat to the Craziest Campaign in American History,” reminds all of us to never count out Donald Trump.

"Mr. Trump’s candidacy was dead when he announced it. (Mexico is sending 'rapists.') His candidacy was dead when he insulted a former prisoner of war named John McCain. ('I like people who weren’t captured.') His candidacy was dead when he cast suspicion on an entire religion. ('Donald J. Trump is calling for a complete and total shutdown of Muslims entering the United States.')," she writes in the New York Times.

"Of all the times Donald Trump was done, it is his current status as a supposedly lame duck first-term president that reminds me most of his final months on the trail. Back then, luminaries in his own party were condemning him, calling on him to drop out and researching a late-race change to the top of the ticket."

It's an important reminder with Trump’s approval ratings are stuck in the 30s — less than a year into his presidency. Then again, unlike in 2016, he doesn't have a true opponent to campaign against and won't for another three years. When you're president, you're running against yourself.