But as those areas have waned, the suburbs of Indianapolis have flourished. The population of Carmel, where 70 percent of the adults have at least a bachelor’s degree, rose from about 25,000 in 1990 to more than 90,000 today. In nearby Fishers, which now has two high schools and an Ikea store, the rise has been even more significant, from 10,000 in 1990 to more than 90,000 now.
For Mr. Donnelly, that makes for fertile territory. He has made 70 campaign appearances in the Indianapolis suburbs, and more than 30 in Hamilton County, where Carmel and Fishers are thriving.
The race has had a highly negative tone, with more than 114,000 ads aired — the most in the nation so far, according to the Wesleyan Media Project. Mr. Donnelly said he would not apologize for fighting back. “If you throw a fastball at my head, I am going to throw one twice as fast at your head. I am not going to take it.”
But mostly, he has tried mightily to persuade voters that he is a “Regular Joe,” traveling the state in an R.V., sometimes wearing flannel shirts, addressing crowds with an empathetic bearing.
In the end, the result may well be determined by the president as much as the candidates.
Robert T. Grand, a lawyer-lobbyist in Indianapolis and a leading Republican, said that he had women tell him they were “appalled” by the treatment of Justice Kavanaugh, and that would help to motivate them to vote for Mr. Braun.
But he also noted: “This is a referendum on the president, no question. And presidents don’t do well in midterms. That’s history, and it doesn’t matter who the president is.”