If there’s one district Trump should win by a mile, it’s the 1st District in northwest Indiana, which is adjacent to Chicago and the soul of Indiana’s steel industry. The district is heavily blue-collar, Democratic, older and racially polarized, all factors that have usually pointed to wide Trump margins. Trump should also do very well in southern Indiana’s 8th and 9th Districts, home to former “Butternut Democrats” — white, socially conservative working-class voters who used to vote Democratic but have swung hard to the GOP. (“Butternut” was Civil-War-era slang for a Confederate soldier; the southern section of Indiana long had sympathies with the rebel cause.)

Meanwhile, Cruz is likely to fare best in the 5th District, situated in the northern Indianapolis suburbs and by far the highest-income district in the state. About 43 percent of white 5th District residents 25 and over hold college degrees — 19 percentage points higher than any other district in the state. In particular, Cruz will need booming Hamilton County — home to many wealthy voters employed in the life-sciences sector — to play a role similar to the one Waukesha County played for him in Wisconsin.

The problem for Cruz is that in a close race, his support could be inefficiently concentrated in one district. The 5th District casts more GOP votes than any other in Indiana; in fact, in 2012 it cast more than twice as many votes for Mitt Romney as its neighbor to the south, the 7th District. Yet like all others, it will award just three delegates. To halt Trump, Cruz probably needs to win at least five of nine districts, or 45 delegates. That looks unlikely today.