There are at least two major surprises to emerge from the opinion survey conducted for the University of Baltimore and Baltimore Sun Media: the failure of the hand-picked successor of Larry Hogan, one of the most popular governors in state history, to dominate the Republican field; and the revelation that Donald Trump would beat Mr. Hogan in Maryland if the two squared off in 2024 for the GOP presidential nomination — by a landslide 2-to-1 margin.

Under the poll, by OpinionWorks of Annapolis, former Maryland Commerce Secretary Kelly M. Schulz, who has been strongly endorsed by Mr. Hogan, has only a modest six percentage point lead over Del. Dan Cox, with 27% of likely voters compared to his 21%.

Under different circumstances, this might seem comfortable. But we would expect that margin to be significantly wider, given Mr. Hogan’s eye-popping approval ratings (a March poll from Goucher College pegged it at 65% of Maryland voters); Delegate Cox’s right-wing extremism (including his effort three months ago to have the governor impeached over how he managed the COVID-19 pandemic); and Ms. Schulz’s successful fundraising that has allowed her TV ads to dominate the airwaves.

It’s clear that Maryland GOP voters are resisting conventional wisdom, and it’s due to Donald Trump.

Oh, that might be a little too facile, but given how Mr. Trump has endorsed Mr. Cox, it’s not far off. And small wonder the former president did. Mr. Cox has been a loyal foot soldier in the Trump-MAGA movement from the Jan. 6 protest at the U.S. Capitol to his declaration that Vice President Mike Pence was a “traitor.” On the “America-first patriot” candidate’s own website, the photo of Mr. Trump is substantially larger than that of Mr. Cox, and his list of “issues” includes a promise that 2020 election results will undergo a “forensic audit.”

The delegate’s emergence as a serious contender might prove short-lived given that 42% of GOP voters are undecided, but Mr. Cox’s early success reflects the enthusiasm of core Trump supporters. This, along with a preference for Mr. Trump over Mr. Hogan in the White House, speaks to a split identity problem for the Maryland Republican Party. It appears Governor Hogan’s brand — a kind of pro-business, anti-tax centrist who prefers to sidestep culture war issues like abortion and can appeal to Democrats and independents — misses the mark with his own party’s voters.

One can see the consequences of this in Ms. Schulz’s campaign materials, which attempt to appeal to both camps by seizing on conservative concerns like “parental rights” without explicitly mentioning critical race theory or transgender students in school bathrooms. She bashes Baltimore for not adequately prosecuting criminals and promises to “treat police like heroes.”

But there is no mention on her website of abortion, or Second Amendment rights or election security or other favored national GOP talking points. This is surely no accident and follows the recent call from Dirk Haire, the Maryland GOP’s chair, for voters to embrace “common sense conservative policies” and not be distracted by “cults of personality.”

The challenge, of course, is that where Ms. Schulz comes off in her TV ads as safe and conventional as she promises not to mandate masks in schools, Mr. Cox sounds like he’s ready to aggressively go after Democrats in Annapolis, down to his slogan, “Free the Free State.” Yet that kind of rhetoric is exactly what could doom the nominee.

Democrats can afford partisanship given the party’s 2-to-1 advantage in voter registration; the GOP can’t — at least not if they wish to capture statewide office. In the general election, Donald Trump lost big in Maryland, with Joe Biden recording a 2-to-1 victory in 2020. If Mr. Cox wins the Republican primary, he is similarly doomed to failure in the statewide race.

That leaves candidates like Ms. Schulz, backed by a governor harshly critical of Donald Trump, to walk the tightrope of general election viability, as fellow Republicans like Mr. Cox unabashedly celebrate their common ground with Donald Trump. For the party’s sake, let’s hope Maryland’s undecided voters are paying attention — and ultimately as pragmatic as the state’s GOP chair.