Donald Trump as a major party presidential nominee seems so fundamentally unlikely that observers are ready to jump at any possible opportunity to proclaim his rise to power over. And the "Super Saturday" results in Louisiana, Kentucky, Kansas, and especially Maine constitute a real disappointment for Trump relative to sky-high expectations.

But make no mistake: He is still winning. A mildly disappointing evening for Trump was also a catastrophically disappointing evening for Marco Rubio, leaving the non-Trump field more divided than ever. Ted Cruz remains a shrewd, oft-underrated politician, but he faces major structural weaknesses in his quest to overtake Trump.

Most notably, the basic reality is that Trump has a lead even though the most Cruz-friendly parts of the country have already voted.

If the Republican establishment had rallied behind Cruz's standard after Iowa and New Hampshire, they might have helped him beat Trump in the South and win the nomination, but they didn't want to. Now Cruz will have difficulty raising money and securing endorsements that other non-Trumps didn't.

Last but by no means least, Cruz's run of good luck has come at a time when he mostly hasn't been attacked by Trump — whose rhetorical fire has instead been aimed squarely at Rubio. A month ago, when Cruz briefly looked like the biggest threat to Trump, Cruz was targeted heavily by Trump, and his standing fell sharply. Then Trump pivoted to Rubio, and he collapsed. If Cruz once again becomes the top threat, he'll face renewed attacks and may fall back again. Nothing is over until it's over, but the nomination is still Trump's to lose.

Ted Cruz's best states have mostly already voted

Cruz is fundamentally a type of candidate whom we have seen in primary campaigns before. He is an evangelical Christian running as the One True Conservative in the race. Not well-liked by the party's key money men, these candidates nonetheless appeal to many grassroots conservative activists. They have an ideological makeup similar to a typical backbench House Republican, and they do well in the kinds of places from which the bulk of backbench House Republicans come — deeply red states with very conservative GOP primary electorates.

Check out the states that Mike Huckabee won in 2008:

Or that Rick Santorum won in 2012:

In the end, these candidates tend to be done in by two things.

One is an inability to carry Texas, which is far and away the largest of the deep red states but whose vast size tends to advantage fundraising and organization on a scale Huckabee and Santorum couldn't pull off. This isn't a problem for Cruz, who is from Texas, is better-financed than his predecessors, and already won the state.

But the other factor is a big problem for Cruz: Republican Party voters in blue states are considerably more moderate than those in red states. This is a difference from the situation on the Democratic side, where there are some conservative states that feature a small number of very liberal Democrats. These relatively moderate blue-state Republican voters don't have much sway in Congress, where they tend to nominate candidates who simply lose the general election, but they matter a great deal in primaries.

The problem for Cruz is that of the 13 states that backed either Santorum or Huckabee in the past two cycles, nine have already voted, and the four that remain outstanding — Mississippi, West Virginia, North Dakota, and Missouri — are small compared with places like California, New York, Illinois, and New Jersey that should be much tougher for him.

The field is divided heading into a crucial 10-day sprint

On Tuesday, Hawaii, Idaho, Mississippi, and Michigan will vote. A week later comes North Carolina, Illinois, Missouri, Ohio, and Florida.

If Marco Rubio and John Kasich dropped out this afternoon, Ted Cruz would have a decent chance at consolidating the conservative vote behind him and beating Trump. Conversely, had Cruz performed poorly in Kentucky and Louisiana and Rubio surprised to the upside, Rubio and Kasich would stand a very strong chance of beating Trump in Florida and Ohio respectively, setting the stage for a three-man Stop Trump effort and a convention fight.

Instead, we got a strong Cruz performance that is encouraging him to argue, accurately, that he is the only non-Trump candidate who has a mathematically plausible path to a majority. At the same time, neither Kasich nor Rubio will drop out until they get a chance to try to win in their home states.

This sets up both contests as three-way races. Cruz is likely to draw significant support in southern Ohio and northern Florida, which means Trump could easily win with as little as 35 percent of the vote. These are winner-take-all elections in big states, so carrying them both would put Trump close to the finish line even with his home turf in the New York/New Jersey area still outstanding.

A lot hinges on how you think about Maine

The counterpoint to this from the Cruz camp is that his success in carrying the Maine caucus on Saturday night shows he's not a niche Southern candidate. Maine is a secular state, after all, that has a clear Democratic lean in national politics. If Cruz can win there, the argument goes, then he can win anywhere.

The other interpretation is that the Maine caucus was a very idiosyncratic event that speaks more to Cruz's organizing prowess than anything else.

Consider that in 2008 Mitt Romney won Maine with 2,837 votes, and in 2012 he did it again with 2,381 votes. Donald Trump got 6,070 on Saturday and lost to whoever mobilized a completely unprecedented 8,550 people to caucus for Cruz. That's more than the total number of people who voted in the previous two cycles.

Even this interpretation, to be clear, is flattering to Cruz. It indicates that he has vastly exceeded what previous True Conservative candidates have been able to do in terms of organization and mobilization. That's bullish for Cruz's chances in future low-turnout caucus states, but the only two left are Hawaii and Utah, so it won't do him much good.

The Republican party is broken