It is in the industrial Midwest, not in the South, where Ted Cruz’s audacious theory of the 2016 race was supposed to be put to one of its most important tests. Michigan’s primary on Tuesday — and especially what happens that day in the Detroit suburbs that in 1980 were ground zero for a new political species, “Reagan Democrats” — will answer this question: Can Cruz locate and motivate legions of recently nonvoting conservatives, millions of them nationwide, especially whites without college experience, who can be pulled back into voting in numbers sufficient to determine the election in November?

But the best-laid plans of mice and men and even senators often go awry, and one problem with Cruz’s plan is that it was formulated in olden days, in the world B.D.T. — Before Donald Trump. He, too, is courting this cohort of the disaffected, whose grievances about politicians certainly cannot this year include being ignored by them. But although Trump may bestride the political scene mastodon, Patrick Colbeck and Wendy Day are undaunted.

Colbeck, 50, was an engineer with no interest in politics until, six years ago, he did something almost unprecedented even among members of the national legislature: He read the Affordable Care Act, aka Obamacare. He concluded that “this is about control and has nothing to do with care.” Now he is a Republican state senator, the first Michigan legislator elected from the tea party, and a thorn in the side of the GOP’s legislative leadership on spending and other matters. Which is to say, he is somewhat like Ted Cruz, of whose Michigan campaign Colbeck is chairman.

Day, 43, is the wife of a soldier who has a Purple Heart from two tours in the Middle East, and the mother of a 19-year-old soldier just back from his first deployment, in Kuwait. She was working with war widows before becoming state director of the Cruz campaign because “he’s been to Babylon and survived.” Meaning he’s resisted “the seductive nature of Washington.” Now she travels with a spreadsheet, supplied by Cruz’s national campaign headquarters in Houston, detailing the expected March 8 vote in all of Michigan’s 4,500 precincts and the number of votes Cruz needs to get in each in order to win the state.

Houston projects that Cruz needs 345,000 of the 1.08 million votes the campaign expects to be cast. Day has on her phone a picture of two of those voters who, with no prompting from the campaign, set up a table outside a tractor supply store to educate voters about Cruz’s enthusiasm for the Second Amendment.

Yes, each such anecdote testifies to Cruz’s ability to energize a passionate cadre, and, yes, as has been said, the plural of “anecdote” is “data.” Today, however, much more than when Winston Churchill said so eight decades ago, “We have entered the region of mass effects.” In Michigan, as in many of the Super Tuesday states, the Cruz campaign mounted the most ambitious efforts to create telephone-and-shoe-leather get-out-the-vote operations, all of which strengthen the sinews of American democracy.

A Detroit News/WDIV-TV poll, taken Feb. 14-16, after Iowa’s caucuses and New Hampshire’s primary but before South Carolina’s primary and Nevada’s caucuses, presented a microcosm of the GOP’s national problem: Trump 25.2 percent, undecided 21.3, Cruz 15, Marco Rubio 11.8, John Kasich 10.5, Ben Carson 9, Jeb Bush 5.3. Trump had the highest unfavorable rating (41.3), but the combined 37.3 percent of the three serious Trump rivals still in the race is too fragmented to derail him.

Michigan’s primary comes a week — an eternity — after Super Tuesday’s 11 primaries altered the political landscape. Michigan is one of the 18 states (and the District of Columbia) — with 242 electoral votes — that Republicans have lost in six consecutive presidential elections, so attention must be paid.