That may be because Mr. Trump’s endorsement is hardly a guarantee of an election victory for his chosen candidate. Take two cases earlier this year. The former president endorsed a Republican in a Texas special congressional election, Susan Wright, who lost in July to another Republican, state Rep. Jake Ellzey. In the Pennsylvania Senate GOP primary, Mr. Trump’s endorsed candidate, Sean Parnell, ended his campaign in November after losing a child-custody case in which his former wife alleged he abused her and their children…

Still, Mr. Trump’s political sway won’t be measured only in primary victories but also in how many of his favorites fare in general elections in swing states and competitive districts. All these candidates face a critical choice: Should they focus on Mr. Trump’s claims that the 2020 election was stolen to protect their endorsement? Or should they make their race about providing a check on President Biden and risk incurring Mr. Trump’s wrath?

This question faces dozens of Republican candidates in Senate, House and gubernatorial races, but the clearest test of Mr. Trump’s message will be races for secretary of state in Arizona, Georgia and Michigan. He backs candidates who are making the alleged theft of the 2020 election their main issue. Is this smart? A Public Religion Research Institute poll from November suggests it isn’t. Its results show that 31% of Republicans, 72% of independents, and 92% of Democrats—and 67% of the overall electorate—rightly don’t believe the 2020 election was stolen. These three secretary of state contests will show the strength of Mr. Trump’s possible 2024 messaging.