Nikki Haley won nearly 130,000 votes in the Indiana GOP primary. Here's what that means for Trump ahead of the general election.

• Donald Trump is on cruise control to formally win the GOP presidential nomination in Milwaukee.
• But ex-UN Ambassador Nikki Haley continues to rack up votes despite her March exit from the primary.

Indiana, which catapulted the political careers of conservatives like former vice presidents Mike Pence and Dan Quayle, is one of the most Republican states in the country.

Since 1940, the state has voted for the Republican presidential nominee in every election except for 1964 and 2008. And former President Donald Trump is virtually assured of winning the state this November, as he also did in 2016 and 2020.

But an interesting thing happened on Tuesday: Trump won the GOP presidential primary, but former UN Ambassador Nikki Haley still won over 20 percent of the vote, despite her March exit from the race.

With nearly all precincts reporting their results, Trump earned 461,663 votes (78.3 percent) to Haley's 128,168 votes (21.7 percent).

Similar to results in states like Virginia and North Carolina, Trump performed strongly in Indiana's rural counties. However, the former president still has a suburban problem, as evidenced by his numbers in the Indianapolis area, with many moderates and GOP-leaning independents continuing to be leery of his 2024 candidacy.

In Marion County — which is consolidated with Indianapolis and is the most populous jurisdiction in the state with more than 965,000 residents — Trump only beat Haley by 30 points (65 percent to 35 percent).

That's a significant drop-off from Trump's nearly 57-point statewide margin, and it's especially notable since the former president has been the presumptive nominee for weeks.

And in suburban Hamilton County, a longtime GOP stronghold which has seen its Democratic vote share soar in recent years, Trump only won by 32 points (66 percent to 34 percent).

In the general election, Biden is favored to win Marion, a county that he carried by a 63 percent to 34 percent margin over Trump in 2020. Meanwhile, Hamilton County will be more of a battleground, as Trump only won it by seven points (52 percent to 45 percent) that year.

So while Trump might see the Indiana victory as a mere formality ahead of the RNC convention in Milwaukee, the national suburban trend is a glaring sign for the former president in an election where the margins are expected to be close in the key battleground states.

While Indiana may be safely Republican in November, suburban voters in Hamilton County will likely vote in a similar manner to other marginally-Republican and swing jurisdictions that will decide the election.

Trump has sought to tout his economic message to these sorts of voters, an area where he has found success in poll after poll. But many suburban voters are also concerned about issues like the preservation of democracy, abortion rights, and environmental policy, which all strongly favor Biden.

And it could give the ex-president a good deal of trouble, especially if he doesn't court Haley's voters ahead of the fall election.