The “common wisdom” is that Donald Trump has the nomination sewn up. Yet, what does he really have? A mere 316 delegates of the total 2,472. That’s only about 25% of what he needs. Meanwhile, Ted Cruz has 226 delegates, or about 18%, and Marco Rubio has 106. Not a commanding lead.

Worse yet, we’re shooting in the dark. We had to guess about some of the Super Tuesday states. Some of the polls were about a half-year old. The upcoming states are even more of a mystery. Yes, Trump seems to have a solid lead in Kentucky and Michigan, but there are no current, reliable polls for Kansas, Louisiana, Maine, Hawaii, Idaho, Mississippi or Washington.

According to the New York Times, on Feb 24:

[The] Donald J. Trump. . .path to the Republican nomination looks wider than ever. But it could still contain pitfalls and roadblocks. Here are some of the ways he could still stumble.

Billionaires get into the game

Top Republican donors have shied away from confronting Mr. Trump, but at some point the party’s bankrollers may get serious about saving it from a man they view as a catastrophe. If they did, this could represent a serious threat to Mr. Trump. Imagine tens of millions of dollars in attack ads blanketing the landscape of primary states.

An alternative emerges

In a race that began with 17 candidates, Mr. Trump has benefited from deftly playing his opponents against one another. With four left, he can still control the race with far less than a majority of the vote. . .But should the field suddenly dwindle to one or two rivals of Mr. Trump. . .it would test the breadth of his support as never before.

Debates turn disastrous

Mr. Trump has staggered through the debates by sheer force of personality, at times inflicting real damage to himself in the process. In South Carolina, late-deciding voters rejected him after his volcanic attacks on former President George W. Bush in the final debate.

A big-state stumble

Mr. Trump has a lead in the delegate count, but ultimately he will need. . .1,237 to clinch the nomination. [His] opponents also have a window to catch up with him, or at least to deny him the majority he needs, by making a stand in big states like Florida and Ohio, where Trump victories might make him truly inevitable.

His own worst enemy

Republicans have bet for months that Mr. Trump would destroy his own campaign through sheer intemperance or incompetence. So far, they have been disappointed. . .But just because Mr. Trump has not yet paid a price for his lack of discipline does not mean he never will. A monumental blunder could be much costlier now than it would have been earlier in the race.

It’s all about momentum. Up to now, it’s all been for Trump. But there has been some stumbling, and momentum can change quickly. We’ve had proportional states so far, which has meant Trump’s wins have not been absolute. If Cruz or Rubio suddenly catch fire, it won’t take many “winner-take-all” states to turn the tide quickly. The race is not over.