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

The chance to stop Trump is real

Two days after Super Tuesday, the GOP establishment’s knives are once again out for Donald Trump -- whether it’s Mitt Romney’s speech today, tonight’s debate in Michigan, or the new TV ads targeting Trump. And here’s the reality: The opportunity to stop Trump is real.

After the Super Tuesday results, it’s clear that Trump had a good (though hardly great) night. Despite winning seven out of the 11 contests, Trump holds just a 23-delegate lead over Ted Cruz from the Super Tuesday delegates, according to NBC’s count: Trump 243, Cruz 220, Rubio 101, Kasich 21. (The biggest reason for this narrow deficit: Cruz absolutely cleaned up winning Texas delegates.)

Overall, the delegate race is Trump 325, Cruz 237, Rubio 117, Kasich 27. So while Trump’s rivals now have 12 days to stop Trump -- especially when it comes to the March 15 winner-take-all primaries in Florida and Ohio -- it’s also pretty obvious that Trump need a win in either Florida or Ohio to have a surer path to 1,237 delegates. These contests no longer look like luxuries for Trump; they’re necessities.

Trump’s rivals have opportunities rack up delegates over the next five days

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And before the March 15 contests, it’s also worth noting that many of the upcoming March 5-8 GOP contests are closed off to non-Republicans, meaning that the independents and outsiders who have been helping Trump at the ballot box won’t be able to participate.

March 5

Kansas (40 delegates): Closed (Caucus)

Kentucky (45): Closed (Caucus)

Louisiana (47): Closed (Primary)

Maine (23): Closed (Caucus)

March 8

Hawaii (19): Closed (Caucus)

Idaho (32): Closed (Primary)

Michigan (59): Open (Primary)

Mississippi (40): Open (Primary)

Indeed, when you look at this calendar and the closed nature of the contests, it looks like an opportunity for Trump’s opponents. Trump is leading in the polls in Michigan, and he should do well in Mississippi (if the Alabama/Georgia results from Tuesday are any indication). But the other closed contests are opportunities for his rivals. Can they take advantage?

Mitt Romney and the GOP’s original sin with Trump

At 11:30 am ET from the University of Utah, former Republican presidential nominee will deliver a speech on “the state of the 2016 race.” But we all know the topic is much narrower -- it’s about Donald Trump. “Donald Trump is a phony, a fraud. His promises are as worthless as a degree from Trump University. He's playing the American public for suckers: He gets a free ride to the White House and all we get is a lousy hat,” Romney is expected to say in his speech, according to advance excerpts. But for establishment Republicans to understand how they ever let Trump into the GOP tent to begin with, it’s worth remembering that Romney publicly accepted Trump’s endorsement, well after Trump’s racially-tinged “birther” crusade against President Obama. “I’m so honored and pleased to have his endorsement,” Romney said on Feb. 2, 2012. Trump was even going to have a role on the first night of Romney’s 2012 convention, but that first night was canceled due to a hurricane. No, Romney didn’t create Trump. But he let him into the GOP’s tent, and Trump is now on the verge of taking it over. And in a way, it looks like Romney’s speech is an attempt to wash away that original sin.

More GOP groups advertising against Trump

If you want to see further evidence about how any GOP group with money is now aiming its cannons at Trump, just look at this new ad from the GOP group Veterans Against The Deal. More from NBC's Leigh Ann Caldwell: “Club for Growth, a conservative anti-tax group, announced a new $1.5 million ad buy in the upcoming primary state of Florida.” What a difference a month makes when it comes to the advertisements against Trump. Of course, it’s worth asking if they would have made a bigger difference coming one or two months ago. (In fairness, Club for Growth earlier ran ads against Trump.)

WaPo: Clinton staffer who set up email server gets immunity

As far as the Democratic delegate race after Super Tuesday, it’s Hillary Clinton 1,017, Bernie Sanders 424 -- meaning that Sanders needs to win 59% of the remaining delegates to reach the 2,383 magic number. The only thing that could stop Clinton getting the nomination? If the FBI doesn’t give her a clean bill of health regarding the emails. The Washington Post: “The Justice Department has granted immunity to a former State Department staffer, who worked on Hillary Clinton’s private email server, as part of a criminal investigation into the possible mishandling of classified information, according to a senior law enforcement official. The official said the FBI had secured the cooperation of Bryan Pagliano, who worked on Clinton’s 2008 presidential campaign before setting up the server in her New York home in 2009. As the FBI looks to wrap up its investigation in the coming months, agents are likely to want to interview Clinton and her senior aides about the decision to use a private server, how it was set up, and whether any of the participants knew they were sending classified information in emails, current and former officials said.”

On the trail

Donald Trump holds a rally in Portland, ME at 1:30 pm ET before tonight’s GOP debate in Michigan… And Bernie Sanders campaigns in Nebraska and Kansas.