The Democratic presidential candidates are debating in Houston on Thursday night, and the chances are that the “electability” chestnut will come up. Which candidate is best positioned to take on President Trump?

The “electability” debate often tends to be hopelessly confused. So if it must come up, let’s hope the candidates try to bring some clarity to it.

For instance, it’s all but certain that former vice president Joe Biden will claim that he’s the candidate best positioned to beat Trump, as he so often does. If so, there’s an opportunity here for his rivals to try to bring that clarity.

Those opponents — like Sen. Elizabeth Warren (D-Mass.), who will face Biden for the first time — will probably try to undercut the case for Biden’s electability. But there are two distinct ways of doing this, each of which brings up a whole different set of issues.

One is to subtly raise questions about Biden’s age and mental sharpness. As Ryan Cooper notes, this could be done indirectly by drawing attention to a verbal pratfall, which could raise concerns among Democrats about Biden’s fitness for a grueling presidential campaign.

Related to this, I’d like to see questions — either from a rival or from a moderator — about Biden’s cavalier treatment of facts and his brash dismissal of criticism of it. How can Biden continue with this and hope to draw a sharp contrast with Trump’s endless lying and with what will be the most propaganda-driven, disinformation-saturated campaign in human history?

Those things should be leading exhibits in the case against Trump’s fitness for the presidency. How will Biden make that case given his own looseness with facts? (No, I’m not drawing an equivalence between their respective treatments of factual reality.)

Another way to raise questions about Biden’s electability concerns political geography and demographics. One foundational idea of Biden’s candidacy is that his “middle class Joe” persona and connections to hardscrabble central Pennsylvania equip him to win back Rust Belt blue-collar whites.

One of his rivals — especially Warren or Sen. Bernie Sanders (I-Vt.)— might properly ask why Biden is better equipped than the more populist candidates to win back those voters.

It’s at least possible that the candidates offering more ambitious agendas for constraining corporate power and revamping international trade relations might make a better pitch to them. After all, Trump promised to take on economic elites and bad trade deals — fraudulently and incompetently, but still — and won the region.

Biden might argue that many of those voters — who are sometimes said to be progressively inclined on economic issues — are actually more conservative and easily alienated by talk of too much government intervention than is commonly supposed. That might actually be true, but the point is, let’s hear him make this case.

Let’s face it: The subtext of the claim that Biden can win those voters is that the aging white guy — the one who arouses the contempt of “woke” progressives with his past flirtations with white-backlash politics and his hidebound stumbles over contemporary sexual mores — has hidden appeal to them.

We need to get this debate out into the open. Why does Biden think he has better appeal to those voters? If it has nothing to do with cultural signaling or wokeness-baiting, and is all about his relative economic moderation, he should say so, and we can have that debate. He’ll say he has some kind of magical middle-class appeal. The populist candidates can say he’s too much of a corporatist to have real middle-class appeal. Let them litigate this openly. This debate is too often shrouded in subtext.

Similarly, the “electability” debate can be expanded. Winning the Rust Belt states might also require energizing young and minority voters, and winning over suburban whites, to offset Trump’s massive advantage among non-college whites. Yes, the more “cosmopolitan” coalition also exists in the Midwest. Instead of talking only about rural whites in diners, let’s hear why Biden would do better with those voters than the energetic, progressive and nonstop-plan-generating Warren would.

Conversely, tough “electability” questions can be directed at Biden’s challengers, too. A Biden adviser argued to reporter Ryan Lizza that Biden has more trans-racial appeal than any rival, winning moderate non-college-educated Midwestern white Democrats and southern African Americans. It’s a reasonable point. What do the progressive candidates say in response?

Or take Warren’s and Sanders’s support for Medicare-for-all. Even some proponents point out that it might be a challenging sell politically, at least at first. As Eric Levitz notes, this is partly because persuading voters of all its hidden benefits actually would pose a serious messaging challenge.

Warren and Sanders often do a forceful job of substantively rebutting attacks on the idea by pointing out the hideous inefficiency and rapacity of private insurance and noting that any additional taxes would replace the high premiums we already pay. Those are good answers, but we could hear more about how they’d effectively make these arguments in the face of a billion dollars of televised lies and demagoguery.

As it is, “electability” is largely an unmeasurable and unpredictable trait, so Democrats probably should vote for the candidate whose ideas and persona excite them most. But if we’re going to have an argument about electability — whether at the Houston debate or elsewhere — let’s have a real one.

Read more:

Greg Sargent: Sotomayor’s brutal dissent unmasks an ugly truth about Trump

Paul Waldman: Why Democratic voters need to stop thinking about ‘electability’

E.J. Dionne Jr.: Like it or not, Thursday’s debate is about electability

Jennifer Rubin: Can we talk ‘electability’ for a moment?

Jennifer Rubin: Trump is the one with the ‘electability’ problem