I think there's a decent argument that Burns's loss in South Carolina was a bit of bad luck. Neither Burns nor Biggs had held elected office before, and neither had significant backing from the state party generally, so that one may have been a bit of a toss-up. As Geoffrey mentioned, Burns had some baggage, so given two unknown candidates, that might have offset the benefit of the Trump endorsement.

But in the Utah Senate race and Colorado's 5th, Trump chose to back outsider-ish candidates rather than those who were supported by other Republican institutions or the party apparatus. Dave Williams was controversial from the start, running as a candidate while maintaining his position as party chair, which many saw as a conflict of interest. And neither Utah nor Colorado have ever been states that were particularly friendly to Trump's bombastic style, so his choice of outspoken MAGA candidates in those races may not have persuaded voters to those candidates.

—Mary Radcliffe, 538

Nathaniel, I think these were Trump’s riskiest set of endorsements so far. All three candidates had some serious weaknesses and they were running against credible alternatives. However, one thing I think is notable is that outside groups had no issue spending heavily against these particular Trump-backed candidates.

In South Carolina, Burns was on the receiving end of several hundred thousand dollars in independent expenditures from groups bankrolled by deep-pocketed GOP donors. Those same groups also spent against Dave Williams in Colorado. And in Utah? Well, Utah is among the least Trump-friendly of the heavily Republican states, and rather than back the more established conservative horse in the race, Brad Wilson, Trump looked further afield. And there was a lot of outside spending to back Curtis as well, while Staggs got little help.

—Jacob Rubashkin, Inside Elections

I'm an Idahoan, so this take might be wildly insular, but I think that Republicans in western states (like Colorado and Utah) are still able to put forward candidates that are conservative enough to ward off Trumpian (typically newcomer) candidates with anti-democratic tendencies, armed with conservative bona fides that still serve what Trumpian conservatism feeds, like anti-establishment, anti-authority authenticity. But it is of a frontier flavor that I think Trump and many Trumpy candidates don't have.

—Meredith Conroy, 538 contributor

It's not exactly breaking news that Trump has a strong hold over the GOP. But if you look at the three cases where his endorsees lost tonight, each pick had potential challenges, either because of their own weaknesses as candidates or strong candidates running against them. In South Carolina's 3rd District, Mark Burns had a controversial past that invited outside spending to help his opponent, and Burns also barely raised any money from donors, mostly self-funding his bid with loans. In Colorado's 5th District, Dave Williams had rubbed a lot of people the wrong way as state party chair, to the extent that outside groups spent more than $2.6 million against him or on behalf of his main primary opponent. And Trump doesn't have as firm a hold over GOP politics in Utah, indicative of how his endorsee, Trent Staggs, couldn't beat out the establishment choice in Rep. John Curtis, who had a stronger track record as an incumbent congressman and received a ton of outside support.

—Geoffrey Skelley, 538