Could it be that in riding the issue of Donald Trump’s “fitness” for the presidency, Hillary Clinton is setting herself a trap? After all, if she wins on that issue, as she may well do, what kind of mandate will she have?

It’s not my intention here to belittle the critics of Mr. Trump’s character. He is the author of his own problems, and there’s no reason for the Clintons (or anyone else) to back off, even if they lack the moral standing to lecture the rest of us.

Nor is it my intention to suggest that the treatment of women isn’t an issue. It’s a big one in this country. If this election throws the question into sharp relief, it will be no small achievement, and make the election of Clinton a famous victory.

On the other big issues in this campaign, not so much. Less than a month from Election Day, it’s hard to think of a single major issue — war, tax policy, immigration, Obamacare, the Supreme Court, Europe — on which Mrs. Clinton has declared for change.

The danger that victory would leave her without a mandate was shrewdly marked in an August column by John Podhoretz. Senator Sanders had a mission, he pointed out, but Mrs. Clinton was running merely to block Mr. Trump.

What kind of mandate would that bring her?

Say what you will about Donald Trump, if he wins he’ll have a mandate. Starting with the blasted wall. I’m against it. Given how many times he’s promised it, though, who is going to be able to say he lacks for a mandate to build such a wall.

Or on cutting taxes in a way that will bring home for investment here the $2.5 trillion that American corporations are hoarding overseas. (They fear the taxes they face if they bring profits back to America. So, like Atlas, they shrug.)

Mr. Trump would have also a mandate to launch a campaign of deregulation. He has constantly been marking this as part of his plan for growth, enabling businesses large and small to start hiring again. It’s a powerful demarche.

Hillary Clinton would have no kind of mandate on that. Nor has she said anything that would give her a mandate on trade. Trump, if he wins, would clearly have a mandate to renegotiate the North American Free Trade Agreement and our other trade pacts.

If it starts a trade war, as we free-traders warn it could, a President Trump would be able to look Congress in the eye and say he has a mandate from the voters. And maybe he’ll be able to tweak the agreements that work a bit more to our advantage.

On matters of a hot war, Mr. Trump has been far more cagey about what he would do, refusing to rule anything out. What Clinton has stressed is what she won’t do — send in American ground troops. What kind of mandate is that?

Mrs. Clinton has suggested a no-fly zone over Syria. But that may be hard to do absent backing from Congress, all the more so after the chaos that followed the failure of President Obama to seek congressional approval for the no-fly zone Mrs. Clinton wanted over Libya.

It’s not that Secretary Clinton hasn’t made promises. Politifact, which keeps track of the candidates’ promises, notes that while Mr. Trump’s list of promises runs to only seven pages, Mrs. Clinton’s compendium of promises runs to something like 40 pages.

But that very number of promises dilutes the sense that Mrs. Clinton would have a mandate for anything major. Her “long and broad list of proposals tend to be incremental,” as Politifact put it, modest “improvements” on Mr. Obama’s domestic policies.

Then again, too, Mrs. Clinton’s foreign policy “largely follows [Mr.] Obama’s” as well. Politifact, which is no right-wing site, acknowledges what has been widely remarked — that “all this makes it hard to find a defining feature of [Mrs.] Clinton’s agenda.”

What if the Democrats were also to win Congress? Absent a mandate for Mrs. Clinton, there’s peril there, too, as the Democrats learned in 2008, when they won both the presidency and control of the House and Senate.

They promptly over-ran their mandate and, on a party-line vote, passed ObamaCare — which even Obama and Bill Clinton now concede has not worked out as hoped. Call it a reminder to mind your mandate — or lack thereof.

This column first appeared in the New York Post.