10:56 – Stepped away for a bit, but taking a last look at the numbers. Cruz has now moved into a narrow second place edge over Kasich in MI with 82% of precincts reporting, but that’s just an edge of 4,000 votes with plenty more left to count. The big news on the other side is that Sanders managed to pull out a win over Hillary in MI, which disrupts the it’s-all-over narrative. Hillary had a big polling lead that seems to have evaporated. and now Democratic officials have to wonder just how solid her polling is elsewhere.

10:00 – Right now, Cruz is moving closer to Kasich in Michigan for second place, 23.8% to Kasich’s 25.5% — but Trump has 37%. Across the aisle, Sanders’ lead keeps going up and down in Michigan, but with 56% of precincts reporting, it’s within two points.

9:54 – Trump just wrapped up a lengthy presser. It was his usual stream-of-consciousness style, but the main takeaway is that he sees himself as the nominee and wants to call for GOP unity behind him. He’s at least a week away from that kind of claim being taken seriously, but other than the moments when it sounded more like an infomercial, the Trump presser worked pretty well for that strategy.

9:00 – Fox calls Michigan for Trump, too, which isn’t too surprising — but it is an indicator that Trump slippage may have been a mirage.

8:52 – Trump’s lead in Michigan has grown to ten points with 18% of precincts reporting, 37.6/27.3 over Kasich, and Cruz has 21.6%. On the Democratic side, Sanders has a 1.7 point lead with 27% of precincts reporting.

8:47 – As one of our Facebook commenters tells me, my confusion on the poll closing times is because polls in Michigan’s Upper Peninsula close at 9 ET, while the rest of the state closed at 8 ET. We’re getting results in faster from the rest of Michigan than we are from all of Mississippi.

8:41 – Doesn’t look like a good night for Marco Rubio. So far he’s below the threshold in Michigan, and he’s not expected to do well in Mississippi.

8:35 – CNN calls MS for Trump too, and Michigan may not be far behind. With 12% (fixed) of the vote in, Trump’s up by seven points over Kasich, and Bernie Sanders has a 3-point lead over Hillary Clinton.

8:29 – Big thanks to Sean Hannity for this!

8:26 – Not a big surprise, except how quickly it happened:

From the exits, it may wind up being a big allocation differential for Trump here. Not much of a Trump slide showing here.

8:17 – Results starting to trickle in from Michigan even though polls are still open in the state. With 3% of precincts reporting, Trump’s less than 200 votes ahead of Kasich. By the way, the previous update was about Mississippi only, which I didn’t initially make clear.

8:07 – Fox is reviewing the exit polls for Mississippi, and it looks like a runaway for Trump. Six in ten GOP voters want an outsider, and 65% of those are going for Trump. Trump’s getting 45% of evangelicals, five points ahead of Cruz. Cruz leads among “very conservative,” but only by 51/40 0ver Trump. That portends a big win and an early call for Trump.

8:03 – Gaaah. Michigan’s polls are open until 9, Mississippi’s have closed at 8 ET. I’ve fixed both cites in the post.

8:02 –  Didn’t take long to make a call for Mississippi, at least for Democrats. Both CNN and Fox called it for Hillary Clinton.

7:59 – Looks like a big turnout in Michigan, according to Daily Caller editor Derek Hunter:

7:55 – Michigan’s polls close at 9 ET, not 8 ET. I’ve fixed the post below.

7:46 pm ET – Nathan Wurtzel brings us the key indicators to watch tonight:

You have to keep your sense of humor.

Original post follows …

Has Donald Trump begun to lose momentum in the Republican presidential primary fight? Has Ted Cruz assumed the mantle of the only viable alternative? Or does Marco Rubio and John Kasich have enough support in these states to make the case that they have what it takes to win the nomination? The first two states in tonight’s four contests may provide us some answers, as voters in Michigan (59 delegates) and Mississippi (40 delegates) cast their ballots in open primaries.

A new poll out from NBC/Wall Street Journal suggests that Trump has indeed lost some momentum — but maybe not enough to be at risk of losing in delegate allocation tonight:

But the Journal/NBC News poll suggests that if the race ever becomes a one-on-one match between Mr. Trump and one of his three Republican rivals, his opponent would have the advantage. In hypothetical head-to-head matchups, Messrs. Cruz and Kasich both lead Mr. Trump, 57% to 40%. Mr. Rubio also beats the Republican front-runner, but by a slightly narrower margin of 56% to 43%.

Perhaps more troubling for Mr. Trump: He is the preferred pick among 36% of Republican primary voters in states that have already held nominating contests, but the field looks more jumbled in states that haven’t yet voted.

With roughly half of the contests still to come, Mr. Trump is the preferred pick of 27% of likely GOP primary voters in those states, with Mr. Cruz right on his heels, at 25%, followed by Mr. Kasich at 24% and Mr. Rubio at 23%.

In other words, it’s a legitimate four-man race, with all four within the margin of error of each other. Trump’s support falls nine points between states that have completed their voting and those yet to come. Fortunately for him, the rest of the field has not partitioned off enough to produce one clear rival, or Trump might be in danger of being eclipsed. Still, given the delegate math at the moment, it would appear that Ted Cruz has the most rational path to beating Trump to 1237.

Tonight’s contests should give us better insight into that question. Michigan has had a significant amount of polling of late, and the RCP average puts Trump up 12 points over Kasich in second place. However, ARG shows Kasich slightly ahead in Michigan, 31/33, with Cruz and Rubio far behind. The threshold for delegate allocation is 15%, but the state GOP has pooled all of them rather than allocate three for each Congressional district. However, if one candidate wins a majority of the vote, then Michigan becomes winner-take-all. That seems unlikely, given the polling, but it would throw a major wrench into the primaries if it did. Right now it looks as though Rubio will get locked out of the delegate allocation; none of the recent polls put him at 15%.

RCP only shows one recent poll for Mississippi, a Magellan Strategies poll conducted on a single day while Ben Carson was still in the race. Trump blows away the competition in that poll, with 41% to 17% for Cruz and 16% for Rubio. The threshold for this proportional-allocation primary is 15%; candidates scoring above that threshold will get a proportional share of 28 at-large delegates. In Mississippi’s four CDs, a majority vote will get all three delegates, and a plurality will result in a 2-1 split with the first runner-up regardless of threshold. It’s the Glengarry Glen Ross allocation: first place is a Cadillac, second place is a set of steak knives, and third place is you’re fired.

The key tonight is whether anyone can pull a victory over Trump in these two states. If he underperforms and ends up in delegate parity with one of his challengers, the Trump Slide narrative will really take off. Two big wins by Trump in the Michigan-Mississippi Mambo probably cools that talk, and perhaps boosts Cruz as the only candidate even within reach of tripping Trump.

Polls close at 8 ET in Mississippi, 9 ET in Michigan. I’ll start live-blogging the results at that time at the top of this post, with the most recent update at the top. John will have a separate thread later in the evening for the Idaho primary and Hawaii caucus, because he’s in Pacific Time, and he’s also Nick The New Guy.