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.

Why Trump’s delegate lead could be even narrower than you think

After five Republican contests over the weekend, Donald Trump has just an 87-delegate lead over Ted Cruz, 392-305. And as one plugged-in GOP rules expert tells us, that lead is probably narrower than that. Why? Well, 112 delegates (representing 9% out of 1,237 needed for the nomination) are unbound because there is NO statewide presidential vote -- like in Colorado. This all underscores, once again, how important the winner-take-all states of Florida and Ohio on March 15 are to Trump’s path to 1,237. They aren’t luxuries, they’re necessities. Here’s the delegate math.

The current delegate count: Trump leads Cruz by 87 delegates

Here's where the race could stand after March 12 (after HI, ID, MI, MS, DC).

And here are some other March 15 scenarios:

Trump needs to win 52% of remaining delegates to reach 1,237 magic number

Trump needs to win 59% of remaining delegates to reach 1,237 magic number

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Trump needs to win 69% of remaining delegates to reach 1,237 magic number

The GOP’s tough choice

Is it better for Trump to wrap up nomination by March 15, or have last week play out for another four months? Right now, the GOP is staring at one of two options: 1) Have Trump wrap up the nomination by March 15 (by winning Florida and Ohio), or 2): Have this rough-and-tumble GOP race play out for another four months, culminating in a highly divisive contested convention.

Romney doesn’t 100% rule out coming to the GOP’s rescue in a contested convention

Here’s the transcript from Sunday’s “Meet the Press” interview with Mitt Romney:

TODD: Let me ask you the way General Sherman was once asked, "If nominated, will you accept the nomination?" If your name is placed in the nomination, and was elected at this Cleveland convention, would you accept it?

ROMNEY: You know, I can't imagine anything like that happening. And I don't think anyone in our party should say, "Oh no, even if the people in the party wanted me to be the president I would say no to it." No one's going to say that. But I can tell you this, I'm not a candidate, I'm not going to be a candidate, I'm going to be endorsing one of the people who's running for president.

ROMNEY: And one of the people, I can guarantee you this, one of the people running for president, one of the four, is going to be the Republican party nominee. Three of the four are people I would endorse. But I'm not running and I'm not going to be running.

Why the delegate math is working against Sanders

If you want to see why Bernie Sanders is facing such a hard climb in making up ground against Hillary Clinton, just consider what happened over the weekend: He won three states (the caucuses of Kansas, Maine, and Nebraska) to her one (Louisiana primary). But out of the four contests, Clinton won more overall delegates, 67-63 -- due to Clinton’s 37-12 delegate win in Louisiana. Here are the allocated delegates from over the weekend:

Kansas: Clinton 11, Sanders 22

Louisiana: Clinton 37, Sanders 12

Nebraska: Clinton 11, Sanders 14

Maine: Clinton 8, Sanders 15

Total: Clinton 67, Sanders 63

And folks, that’s just among pledged delegates, where Clinton has a 199-delegate lead over Sanders, 669 to 470. And among all delegates (when you add the superdelegates), it’s Clinton 1,100 and Sanders 492.

Sanders comes out swinging on trade, Clinton follows with counterpunches on the auto bailout and Ex-Im Bank

MSNBC’s Alex Seitz-Wald: “Sunday night's Democratic presidential debate in Flint, a city where manufacturing jobs have been replaced by poisoned water, should have been on Bernie Sanders' turf: a discussion of trade policies, corporate greed and government spending cuts that have led to horrible consequences.” The problem for Sanders: Hillary Clinton counterpunched on the auto bailout and Export-Import Bank -- and she landed some blows. “I'll tell you something else that Sen. Sanders was against. He was against the auto bailout. In January of 2009, President-Elect Obama asked everybody in the Congress to vote for the bailout. The money was there, and had to be released in order to save the American auto industry and four million jobs, and to begin the restructuring. We had the best year that the auto industry has had in a long time. I voted to save the auto industry.” More Clinton: “One of the ways jobs were brought to, and grown here in Michigan was through something called the Export-Import Bank which helped a lot of businesses, particularly small businesses, be able to export around the world. Sen. Sanders opposes that.” And per NBC’s Kristen Welker, the Clinton campaign is up with a radio ad in Michigan on her auto bailout counterpunch. “On Tuesday, March 8th, vote for the one candidate who stood up for the auto industry……and came through for Michigan …when it really mattered. Hillary Clinton.” So much for Sanders is riding on the outcome of Tuesday’s Michigan contest.

NBC/WSJ/Marist poll: Trump, Clinton ahead in Michigan

Donald Trump and Hillary Clinton are leading their competitors by double digits in Michigan's March 8 primary, according to an NBC News/Wall Street Journal/Marist poll released on Sunday morning. In the Republican race, Trump gets support from 41% of likely primary voters -- followed by Ted Cruz at 22%, Marco Rubio at 17% and John Kasich at 13%. In the Democratic contest, Clinton leads Sanders among likely primary voters by 17 points, 57%-40%. But the race is closer among the larger potential Democratic electorate -- Clinton at 52% and Sanders at 44%. In hypothetical general-election matchups in Michigan, Clinton leads Trump by 16 points, 52%-36%, while Sanders is ahead by an even wider margin, 56%-34%. Against Ted Cruz, Clinton’s lead is seven points, 48% to 41%, while Sanders is up 18 points, 54% to 36%. President Obama’s approval rating in Michigan stands at 50% among registered voters.

On the trail

Hillary Clinton spends her day in Michigan, hitting Grand Rapids and Detroit, while her husband Bill campaigns in North Carolina… Bernie Sanders makes stops in Kalamazoo, Dearborn, and Ann Arbor, MI… Donald Trump holds rallies in Concord, NC at noon ET and Madison, MS at 8:00 pm ET… Marco Rubio spends his day in Florida… And John Kasich stumps in Michigan.

Countdown to HI (GOP), ID (GOP), MI, MS contests: 1 day

Countdown to FL, IL, MO, NC, OH contests: 8 days