Will the Democrats finally have a real debate about immigration this week? Or has the moral outrage surrounding the topic made it too dangerous to discuss in any meaningful way?

When it comes to immigration, there is an apparent disconnect between the increasingly left-wing posture of the party, as represented by its presidential aspirants, and the views of the voting public. In the first Democratic debate, Julian Castro laid down a marker in calling for the decriminalization of unauthorized entry, while all 10 participants in the second debate raised their hands to endorse providing health insurance to unauthorized immigrants at public expense (something ObamaCare pointedly did not provide for). Since then, Sen. Elizabeth Warren (D-Mass.), the frequent policy pace-setter, put forth an immigration plan consisting entirely of liberalizing elements, including decriminalization of unauthorized entry and a substantially more generous approach to asylum. Other candidates, like Sen. Cory Booker (D-N.J.), have followed suit with plans of their own to virtually eliminate detention for immigration violations, and more generally to liberalize our immigration regime.

Such proposals appear to amount to a de-facto open borders policy. Decriminalization of unauthorized entry, plus a generous approach to asylum, would make it relatively easy to enter America. In the absence of a national I.D. card and serious employer sanctions for hiring unauthorized immigrants, it would also be very easy to stay. Taxpayer-provided health care would make it easier still. While even the most liberal major candidates have not endorsed open borders as such, neither have they taken the opportunity to distinguish how their policies would be different from an open borders approach, nor to make any case for the necessity of some distinction between citizen and non-citizen, or of the sovereign right of every country to decide who can join the polity.

This exceptionally liberal stance of the candidates contrasts sharply with the still liberal views of the public — and even of Democratic voters. The general electorate is considerably more conservative. While a path to citizenship for immigrants who are already living in the United States without authorization is overwhelmingly popular among Democrats (84 percent supported it in a recent poll) and attracts very wide support from independents as well (67 percent), decriminalizing unauthorized entry polls much worse: Just 45 percent of Democrats and 24 percent of independents support such initiatives. Even among self-identified progressive Democrats and Democratic-leaning independents, only a slight majority (54 percent) favor decriminalization. After the last Democratic debates, the country's oldest Hispanic organization even went on record warning Democrats that they were going too far.

Why, then, has the Democratic field marched nearly shoulder-to-shoulder leftward? Part of the answer lies in the moral case for the liberal position on immigration. The current surge in migrants from Central America is dominated by people fleeing ongoing civil and personal violence of various kinds. The journey is risky enough that it is insulting to minimize the conditions that have prodded so many to undertake it. Moreover, while past migrant waves were dominated by adult men seeking employment, the current surge includes large numbers of women with young children. Finally, the fact that the Trump administration's cruelty at the border appears to be failing — even as a deterrent — bolsters the case against any enforcement-led approach to immigration.

It's easy to follow our morals down a chain of reasoning that ends with a de-facto open borders policy: If we have a moral obligation not to turn our backs on needy people coming to us for help, then we have a moral obligation to offer asylum to these people on generous terms. And if we offer asylum, why not let them work? Why not provide them with health care? How would keeping immigrants sick and unemployed benefit Americans? And on and on.

But talking yourself into a moral stance is not the same thing as talking a majority of voters into it, nor proving that such a majority will be durable in the face of the potential consequences of such a radical liberalization, like rapidly increasing migration flows. Many of the candidates who have advocated liberalization have also called for dramatically increased aid to Central America to attack the root causes of migration. But even if such a highly speculative project were to succeed, which is far from certain, the Northern Triangle is not the only troubled region in the world. Migrants from considerably farther afield are already crossing the oceans in hopes of finding refuge in America, even under Trump. With 70 million displaced persons and rising, the pool of potential asylum seekers is deep and vast.

The sheer magnitude of the problem is a key component of the moral case for liberal immigration policy. But it is also a key component of the case for conservatism — for not making open-ended commitments with consequences that are difficult to measure. Advocates of a radically open immigration regime need to address the consequences internally before trying to convince others their stance is sound. Otherwise, the conviction behind the stance itself is actually quite fragile, and this will make liberals reluctant to see it challenged.

Increasingly, that appears to be the dynamic driving Democratic non-debate. The left-wing position is grounded in moral outrage at cruelty to innocent children, and the determination to give no quarter to concerns about the cost or consequences of doing the right thing by those in need. Those who harbor those concerns, meanwhile, prefer to hold them quietly rather than to voice them and be denounced.

I had hoped that former Vice President Joe Biden would prove an exception here, that he would be willing to defend a moderate, Obama-style approach to immigration: enforce the border but provide a generous path to citizenship to those who have already put down roots in America. He could point out that an asylum regime that allows migrants to shop for the most generous country in which to settle undermines the purpose of that regime — to ensure that people fleeing war and persecution can find a safe haven — by clogging the system with migrants who don't fit that definition. And it undermines support for the regime among a citizenry that doesn't want its generosity taken advantage of. Biden, or someone like him, could make a case for revising the U.S. immigration system in concert with other developed nations.

Such a proposal may fail — as might Biden's candidacy — but it needs to be aired within a Democratic primary, because it reflects the views of many of the party's own voters. But so far, Biden's preferred approach has been to dance around the subject, posturing as an opponent of Trump's cruelty without making clear how he differs fundamentally from either the administration's restrictionism or his primary opponents' increasingly liberal approach. And no other major candidate has jumped into the breach.

That's a problem. A debate in which widely-held views are treated as anathema does little to convince anyone. It certainly won't convince skeptics that those advocating for dramatic change have really thought their views through. And immigration liberals need to win over those skeptics if they are to succeed in building popular support for the most dramatic liberalization of American immigration policy since 1965 in the face of global populist winds blowing strongly the other way.