Tuesday's Republican primary was a life-or-death moment for Ohio Gov. John Kasich, who had promised to throw in the towel if he didn't win his home state. His victory there was buoyed by spending from the super PAC New Day for America, which concentrated the bulk of its recent spending on ad buys to shore up the state as a Kasich stronghold.

The pro-Kasich group was the biggest ad buyer on the GOP side in Ohio, accounting for more than one-third of overall ad spending in the state's Republican primary, according to the New York Times. Some recent ad buys focused on Kasich's economic record in the state, touting job creation and higher wages.

GettyImages-515623554 Gov. John Kasich speaks on the eve of the Ohio primary at a rally at Westerville Central High School on Monday, March 14, 2016. Photo: J.D. Pooley/Getty Images

The last-minute ad blitz may have given Kasich a boost. Fox News exit polls found that Kasich did better among voters who said they had made up their minds only recently.

The hard-fought primary also turned out a large number of non-Republicans. The Ohio Republican primary is open, meaning that people of any party affiliation can vote in it. Exit polls found that more than one-third of GOP primary voters this year were not, themselves, members of the GOP; 28 percent were independents, and 7 percent were Democrats. Democratic voters favored Kasich over Trump by double digits. 

It's not clear whether they crossed party lines strategically, in the hope of blocking Trump, or whether they would support the Republican candidate over (presumably) Hillary Clinton in the general election in November.