Most of the standout moments during the Democratic presidential debate on Tuesday night involved Sen. Bernie Sanders or Sen. Elizabeth Warren teeing off against someone nobody has heard of.

But these exchanges about decriminalizing illegal entry into the United States, replacing union health plans with a new government-run plan, providing public health benefits to unauthorized immigrants, and other topics that pit activist priorities against public opinion are critical to the 2020 primary.

The problem is that the candidates taking the more moderate stance on these issues relative to Warren and Sanders — Rep. Tim Ryan, former Rep. John Delaney, former Colorado Gov. John Hickenlooper, and Montana Gov. Steve Bullock — are not even remotely central to the 2020 primary. But that’s not because moderates have become marginal in the Democratic Party. It’s because former Vice President Joe Biden, who sits at the top of the polls and broadly agrees with Ryan, Delaney, Hickenlooper, and Bullock — wasn’t on the stage. Biden won’t appear until Wednesday night, in the second night of the debate.

So the debate between the current frontrunner and self-proclaimed successor to Barack Obama and his leading critics on the left happened only by proxy. Someday, one hopes, we’ll get a proper debate. But for now we need to wait.

An annoying debate Democrats need to have

CNN’s moderators framed some of the big policy debates inside the Democratic Party around narrow, technical questions that aggravate liberals.

For example, moderators picked out the least popular pieces of the health care debate over Medicare-for-all. The plan does controversial things like replace private plans and raise taxes but would also eliminate all premiums, all copayments, and all deductibles — stuff that polls really well!

Moderators also pressed on whether candidates would switch illegal entry from a criminal offense to a civil one. This is, at the end of the day, a pretty peripheral question in immigration policy. The DREAM Act, a path to citizenship for 10 million more long-term resident unauthorized Americans, President Donald Trump's squandering of America’s leading role as a destination for foreign-born students, and the future of legal immigration are all much more important issues on substance.

At the same time, there is an absurd conceit from some on the left that if all Democrats just agree to avoid using “Republican talking points” on these questions, then they can sneak into the White House without confronting them. Republicans will obviously use Republican talking points on these topics. Democrats need to decide whether they really want to run on these policy commitments, and if they do, they need to stress-test their talking points and counterarguments. Which they did — but only sort of.

Progressives faced down weak opponents

There is probably some wisdom to be gleaned from the reality that the biggest proponents of progressive policies on the stage hold safe blue Senate seats from New England while the former governor of Colorado and the governor of Montana are skeptical.

So is a very electorally successful senator from the blue-leaning state of Minnesota, and the former holder of a somewhat swingy House seat in Maryland. The mayor of the fourth-largest city in Indiana knows he’s much too liberal to run statewide, and that’s why he’s running for president despite a skimpy résumé. Beto O’Rourke, similarly, impressed a lot of people with his Texas Senate run, which — precisely because it was impressive — tended to demonstrate that his ideas are simply too left-wing for Texas.

It would be silly to conclude from this that Sanders or Warren is “unelectable.” Donald Trump holds lots of unpopular positions, and while ideology and issues matter in elections, they only matter a modest amount.

But the question is important: Do Democrats really want to carry the extra electoral weight of a certain number of unpopular left-wing ideas that are almost certainly not going to be implemented, no matter who wins the election? It’s just that having the argument with Ryan and Hickenlooper felt unimportant because Ryan and Hickenlooper are extremely unlikely to become the nominee.

Delaney did an admirable job of standing his ground and articulating his view, but there was still something vaguely absurd about him going toe-to-toe with Warren. He’s just too overmatched in terms of star power, fame, charisma, fundraising, depth and breadth of staff work, and all the rest. It created an atmosphere in which progressives dominated the stage and moderates looked marginalized. But it wasn’t reality.

Joe Biden won the debate

There’s a reason Delaney — or a more plausible candidate like Bullock or Klobuchar — isn’t doing better. And it’s not his ability to win an argument with Warren and Sanders.

It’s that the vast majority of the people who agree with him support Joe Biden. Reasonable people can disagree as to whether proponents of moderation are well served by having a septuagenarian Washington insider rather than a two-term Montana governor or a younger but experienced woman from Minnesota serve as their champion. But for now that’s clearly what Biden is, and you’d expect the VP from a popular and successful recent administration to be a strong candidate.

Biden is not just a strong candidate, he’s currently leading the race — and by a pretty large margin. The view on display Tuesday night of two New England progressives taking center stage and shooting down all comers was powerful but doesn’t reflect the actual state of the primary. The central figure is Biden, the progressives are taking potshots at him, and so far, he’s holding them off in opinion polls and dominating in endorsements.

That’s the actual state of the Democratic primary, and it’s difficult for debates to move the conversation forward unless the frontrunner engages with his main critics not on aspects of 1970s civil rights policy but on the big issues of 2020. It didn’t happen in the first debate, and the structure of the second one makes it essentially impossible. That means round three, when the roster will narrow and the format will shift to a single stage, will in most respects be the first real contest of the season.