Unlike Mr. Walsh, in particular, his candidacy is unlikely to be just, or mainly, about Mr. Trump. Instead, his candidacy is likely to be dedicated to the issues that have motivated and impassioned him for years — particularly issues related to fiscal restraint and responsibility. He happens to be on the right side of those issues, and the president on the wrong side. Also unlike Mr. Walsh, Mr. Sanford is not in the race to give Never Trumpers a home, nor to instinctively, reflexively oppose the president or “stick it to him.” Indeed, on some issues he will probably agree with him, and not in a tokenist way.

Unlike Mr. Weld, Mr. Sanford has been a big-name player and an elected official in Republican politics in the Trump era, the Tea Party-dominated period that preceded it and the two decades before that. He remains beloved by many conservative activists, who know he’s been serious about reining in wasteful spending, targeting debt and the deficit, and supporting free trade. They remember when he brought squealing piglets to the state house to make a point about “pork” spending. They know he got As and Bs from the Cato Institute for his fiscal record as governor. They know he has a lifetime 93 percent grade from the Club for Growth (which is better than the House Freedom caucus chairman Mark Meadows’s lifetime grade). And they regard him as having had about the least-scandalous scandal in modern political history (he had an extramarital affair because he fell in love and got engaged to the woman).

That, collectively, could make him dangerous — an irony for a candidate who doesn’t seem intent on damaging Mr. Trump. Mr. Sanford really just wants to bring focus to a few big topics and provide some comfort to fellow Republicans who don’t revile the president or even disagree with him on most things but who fret about the national debt and the effects of a trade war, the way most Republicans used to.

How many of those voters are there? If the era of Trump has shown us anything, it’s that Republicans talk a good game about debt and deficits, but when given control of the House, the Senate and the White House, they will pile them up just about as badly, and maybe worse, than a Democratic House, Senate and president would.

It has also shown us that Republicans really do follow their leader — validating the comment that the MSNBC host Chris Matthews has been known to make that Democrats fall in love and Republicans fall in line. But conservative elites who loved Mr. Sanford in 2008, or 2010, or 2012 right through his narrow 2018 primary loss to Katie Arrington, a more Trumpy candidate, will be hard-pressed to dump him now.