Ted Cruz crushed Donald Trump in the Wisconsin primary , winning 48% of the vote to Trump's 35%.  More importantly Trump is going to receive only 3-6 of the 42 delegates at stake, making his path to 1,237 delegates before the convention highly problematic.

Trump will have to win more than 60% of the remaining delegates at stake in order to arrive in Cleveland with a majority.  Since he has yet to crack 50% support in any state so far, the prospect of a bloody convention fight for the nomination looms over both candidates.

In Wisconsin, Nate Silver explains why it's not so much important that Trump lost, but rather how big was Cruz's win:

Clearly tonight’s results were problematic for Trump in terms of his delegate math. A few weeks ago, we’d projected Trump to win 25 delegates in Wisconsin. It looks like he’ll only get 3 to 6 instead. After also accounting for Trump’s failure to get any delegates in Utah last month, our estimate would now project him to get 1,179 to 1,182 delegates total, or somewhere between 55 and 58 short of the 1,237 he’d need to clinch the nomination. Trump could potentially make up the difference by persuading uncommitted delegates to vote for him, although given how poorly Trump’s doing in the delegate-wrangling business, that might not be easy.

But the more immediate question — the one I’m not quite ready to answer — is what tonight tells us about how Trump might perform in subsequent states. Are we overestimating him in Indiana? (Probably.) Underestimating him in New York? (Possibly.) And what about California?

In some ways, though, this misses the big story in Wisconsin. What was really different about tonight is not how poorly Trump did, but how well Cruz did.

Trump will win around 34 percent of the vote tonight. Compare that to his previous results in the four states that border Wisconsin. His results were a bit worse for Trump than in neighboring Illinois and Michigan — not a good sign for him since Rubio dropped out after those states voted. Trump got a higher share of the vote in Wisconsin than he did in the early caucuses in Iowa and Minnesota, however. Overall: 34 percent of the vote was mediocre-to-poor for Trump, but not terrible for him.

But it’s Cruz who had the breakthrough, getting 49 percent of the vote as compared to between 25 and 30 percent in the four Wisconsin border states. Cruz also won all sorts of demographic groups that he doesn’t usually win.

Maybe that means Cruz has finally emerged as the singular alternative to Trump and that Kasich — who’s won only his home state of Ohio — will fade further into the background. Or maybe it means that Republican voters are behaving tactically in order to stop Trump, and could vote for Kasich in states and congressional districts where he runs stronger later on. 

If Trump is stopped, it will not be because of any success achieved by the #NeverTrump movement.  Trump has shown himself to be his own worst enemy, and his gaffes last week as well as the growing realization of how truly "un-Republican" his position on the issues has become will play a far bigger role than any establishment-led effort to derail him.

That said, perhaps the biggest takeaway from the Wisconsin primary is just how far the Trump camp is wiling to go to win the nomination.  Roger Stone, who has become something of an unofficial spokeman for the candidate, told a radio interviewer that the campaign was going to give its supporters the hotel room numbers of anti-Trump delegates:

"We’re going to have protests, demonstrations. We will disclose the hotels and the room numbers of those delegates who are directly involved in the steal," Stone said Monday in a discussion with Stefan Molyneux on Freedomain Radio, as he alleged that Trump's opponents planned to deny the democratic will of Republican primary voters.

"If you’re from Pennsylvania, we’ll tell you who the culprits are. We urge you to visit their hotel and find them. You have a right to discuss this, if you voted in the Pennsylvania primary, for example, and your votes are being disallowed," Stone said.

Stone, a Nixon acolyte and master of political dirty tricks, has claimed at various points that the political establishment is trying to steal the Republican nomination from Trump, with whom he formally parted ways last summer but remains an informal adviser of sorts. He's now vowing "days of rage" on the banks of Lake Erie if the Republican Party tries any funny business at the convention in Cleveland.

“They’re trying to steal it in two different ways. It is interesting to me that in every primary or caucus where Ted Cruz won, we have certified, proven, sworn evidence of massive voter fraud, which will later be presented to the credentials committee in Cleveland in an attempt to unseat delegates who were illegally elected," Stone claimed.

I wouldn't be surprised if Stone's convention operation didn't hand out baseball bats to further "persuade" anti-Trump delegates to change their minds.

Trump's statement after his Wisconsin loss shows that this has gone far beyond politics and is becoming personal:

Donald J. Trump withstood the onslaught of the establishment yet again. Lyin’ Ted Cruz had the Governor of Wisconsin, many conservative talk radio show hosts, and the entire party apparatus behind him. Not only was he propelled by the anti-Trump Super PAC’s spending countless millions of dollars on false advertising against Mr. Trump, but he was coordinating `with his own Super PAC’s (which is illegal) who totally control him. Ted Cruz is worse than a puppet— he is a Trojan horse, being used by the party bosses attempting to steal the nomination from Mr. Trump. We have total confidence that Mr. Trump will go on to win in New York, where he holds a substantial lead in all the polls, and beyond. Mr. Trump is the only candidate who can secure the delegates needed to win the Republican nomination and ultimately defeat Hillary Clinton, or whomever is the Democratic nominee, in order to Make America Great Again.

That doesn't sound as if the dealmaker Trump is open to any kind of deal in Cleveland.  In fact, it's the old Hitler tactic of claiming that his campaign is being "stabbed in the back."  It's the whine of losers in banana republics and now – apparently – America.

Trump's argument that he's the only candidate who can get a majority of delegates before the convention is losing its luster with every Cruz win.  There will now be a hiatus from primaries until the New York contest on April 19.  Meanwhile, Cruz continues to bedevil Trump by wrapping up almost every single uncommitted delegate and fighting for pledges of support from delegates on the second ballot.  He's running rings around Trump in the wrangle over delegates, and it will probably cost Trump the nomination.