On so-called "Mega Tuesday," Democratic candidate Hillary Clinton swept Florida, Illinois, North Carolina and Ohio; Donald Trump, on the Republican side, took home Florida, Illinois and North Carolina.
John Kasich won in his home state of Ohio, keeping alive the dream of a contested Republican convention for those in the GOP who are desperate to stop the rise of Trump.
Bernie Sanders had hoped to upset Clinton in Illinois and Ohio, riding the same wave of white blue-collar voters who took him to the top in Michigan, but couldn't repeat the feat.
Marco Rubio, meanwhile, dropped out after a dismal showing in his home state of Florida.
But there were five states up for grabs on Tuesday — what about Missouri? As of 6:30 a.m. PDT, it's still too close to call: the Democratic race has Sanders and Clinton essentially tied, while Trump and Ted Cruz are in a dead heat for the Republicans.
Here are five headlines that break down the results:
John Kasich survives Ohio primary battle with Donald Trump. Now comes the really tough part.
The Ohio governor won his home state's Republican presidential primary Tuesday, claiming all 66 delegates up for grabs. Kasich now has a chance to block real estate mogul Donald Trump, the front-runner who has many party leaders in a panic over the prospect of his nomination.
But it is a slim chance. It depends on Kasich and the GOP establishment executing a near-flawless strategy in the coming weeks and months. And if this year's race has taught us anything, it's that even the best laid plans can melt under the flame of Trump's unpredictable candidacy.
If this is, as Trump's foes believe, a battle for the soul of the Republican Party, it's now more likely than ever before that it won't be resolved before the convention begins July 18 in Cleveland.
Trump: 'I think you'd have riots' if contested convention results in a different nominee
Republican presidential front-runner Donald Trump said Wednesday that a contested GOP convention could be a disaster if he goes to Cleveland a few delegates shy of 1,237 — and doesn't leave as the party's nominee.
"I think you'd have riots," Trump said on CNN.
Noting that he's "representing many millions of people," Trump told host Chris Cuomo: "If you disenfranchise those people, and you say, 'I'm sorry, you're 100 votes short' ... I think you'd have problems like you've never seen before. I think bad things would happen."
Clinton wins big: Illinois, Ohio, N.C. and Florida all go her way
Clinton had been expected to win the South, but the bigger battleground was in the Midwest. Her Ohio victory short-circuited Sanders' hopes of converting a surprise win in Michigan last week to a sweep of industrial states voting on Tuesday. Adding Illinois to the win column means she carried at least four of the five states that voted Tuesday, shifting the narrative back to her inevitability as the Democratic nominee.
Polls had showed Sanders narrowing her advantage in the Buckeye State, and he predicted he would win Ohio. Sanders had also hoped to benefit in Illinois from Clinton's association with unpopular Chicago Mayor Rahm Emanuel. In the end he could not declare a win anywhere.
How Marco Rubio's campaign collapsed after never really taking off
What Rubio hadn't counted on — what nobody counted on — was Donald Trump. ...
The celebrity mogul usurped Rubio's TV strategy, getting more free coverage than any candidate in history by giving freewheeling speeches and unpredictable news conferences. Suddenly, the most media-friendly candidate wasn't the boyish 44-year-old Cuban American from Miami. It was the brash 69-year-old reality-TV host from New York.
Rubio couldn't compete with Trump on air time — or with Texas Sen. Ted Cruz in organization.
How close was yesterday's presidential primary in Missouri?
If you live in Missouri and didn't bother to vote in yesterday's primary, you're an idiot.
Less than 2,000 votes separated the first and second choices on both the Republican and Democratic ballots — that's fewer than 1,800 votes separating Donald Trump and Ted Cruz on one side and Hillary Clinton and Bernie Sanders on the other, or less than one-half of one percent in both cases.
At this point, Clinton and Trump are the Missouri winners. Clinton took 49.6 of Democratic votes, compared to 49.3 percent for Sanders. Trump took 40.8 percent, with Cruz notching 40.6 percent.
But even CNN isn't calling it yet; there will almost certainly be a recount.