In Mario Cuomo’s famous phrase, leaders campaign in poetry and govern in prose. But as Donald Trump is finding, sometimes the gap is larger still—more like translating across languages.

Take one of Trump’s central policy planks since last fall: excluding people who might pose a risk of terrorism from entering the United States. The Republican nominee has run through a range of different versions of the policy, working to transform an idea that resonated strongly with his voters during the Republican primary into a workable proposal—so far, with minimal success. His latest swing, proposing an unusual ideological test, is part of a foreign-policy speech Trump delivered in Youngstown, Ohio, on Monday.

Trump first announced he wanted to ban Muslims from entering the United States in the wake of the San Bernardino shooting. Initially, it appeared that the proposal could encompass barring even American citizens who are Muslim and traveling abroad from reentering the country. The campaign eventually scaled that back to involve apparently only non-citizens and non-permanent residents. That proposal was widely decried as unworkable—it would overwhelm the immigration system, officials said, and besides, couldn’t respondents simply lie about their religion?—and likely unconstitutional because of its religious test; in any case, it seemed to violate American principles.

In a later iteration, therefore, Trump said he would ban immigration from countries with a track record of terrorism. Trump more or less admitted this was a sham: “People were so upset when I used the word ‘Muslim.’ ‘Oh, you can’t use the word “Muslim.”’ Remember this. And I’m OK with that, because I’m talking territory instead of Muslim.” The switch circumvented the religious test, but raised other problems. For example, would it prevent immigration of people from Britain, France, or Belgium, countries that have grappled with a series of terrorist attacks? Trump was vague. At one point, he said that Muslims from Britain would be acceptable.

Meanwhile, the territory-based idea created other problems. The plight of Christians in the Middle East, who have been persecuted by ISIS, al-Qaeda-linked groups, and others, is a popular cause with Christians in the United States, particularly the conservative ones who form an important part of the Republican base. The plight of Jews in Muslim countries is also a treasured cause. That created a bind for Trump’s running mate Mike Pence, as my colleague Emma Green reported. Pence needed to defend Trump’s policy without appearing to be abandoning persecuted Christians. A Pence spokesman later said that he would support the creation of “safe havens” where Christians and Jews could be protected while being vetted.

The idea of safe havens for refugees is not new, but it has proven tricky to implement. It is either extremely costly and logistically challenging, or else it tends toward failure and tragedy, as occurred with inadequately protected UN “safe areas” in Bosnia during the 1990s.

Trump’s latest idea is to focus on individuals themselves. The AP reports that those seeking to enter the U.S. would be queried on their stances on issues like religious freedom, gender equality and gay rights: “Through questionnaires, searching social media, interviewing friends and family or other means, applicants would be vetted to see whether they support American values like tolerance and pluralism.”

He was somewhat more vague in the speech itself:

In the Cold War, we had an ideological screening test. The time is overdue to develop a new screening test for the threats we face today.

In addition to screening out all members or sympathizers of terrorist groups, we must also screen out any who have hostile attitudes towards our country or its principles—or who believe that Sharia law should supplant American law.

Those who do not believe in our Constitution, or who support bigotry and hatred, will not be admitted for immigration into the country. Only those who we expect to flourish in our country—and to embrace a tolerant American society—should be issued visas.

It’s an interesting approach, not least in the items Trump’s advisers have named as criteria. Trump has struggled to support religious freedom, not least with his initial Muslim immigration proposal. He has struggled with tolerance more broadly, for example offering a highly dubious definition of free speech and calling for stricter libel laws. Trump might be in the position of demanding that those seeking to immigrate to or seek refuge in the United States uphold values that he himself seems ambivalent about.

The focus on tolerance points to one of the great paradoxes of immigration in liberal democracies. By insisting that immigrants follow certain, particular values, Trump is aligned with the anti-immigrant right in Europe, a constellation of populist political parties that have lobbied against “multicultural” conceptions of society. Their supporters argue that there is a tension between values: On the one hand, societies in Western Europe and the U.S. have tended to view welcoming beleaguered immigrants in as a moral imperative. But what happens if Enlightenment values of tolerance and democracy produce an influx of people who are not committed to those values, and who irreversibly change the body politic to eventually undermine them? For these groups, and for Trump, certain measures of intolerance are vital for ensuring tolerance. Their opponents contend that to say so is to step down a slippery slope.

Ideological tests for admission to the country are not new. As far back as the Alien and Sedition Acts in John Adams’s presidency, U.S. policymakers have sought to restrict who can and cannot enter the country, remain in the country, or become a citizen. In 1903, Congress banned anarchists from entering the United States after a worldwide outbreak of anarchist violence. Currently, anyone wishing to become a citizen or a permanent resident is asked whether he or she is or has ever been a member of the Communist Party, a totalitarian party, the Nazi Party, or a terrorist organization. Applicants for asylum are asked whether they have been members of political parties, guerrilla groups, or paramilitary organizations.

These questions are somewhat straightforward: They exclude people based on whether they are members of groups that seek the overthrow of the U.S. government and political system. Trump’s suggestion is murkier, and goes beyond a simple exclusionary test. For example, plenty of Americans oppose gay rights and even gender equality, and while it isn’t hard to find progressives willing to label those views “un-American,” they are also constitutionally protected views for citizens and residents, and within mainstream discourse.

An ideological test such as this presents two major risks of manipulation, one each by the asker and the answerer. From the government side, an ideological test can quickly be turned to questionable purposes, and interpretations can vary widely. For example, many Republican regard the argument that women are underpaid for the same work as men as a canard. Would agreeing with them get a prospective immigrant blacklisted? From the other side, wouldn’t it be relatively simple for an applicant to simply lie?

What unites all these caveats is a question of the extent to which Trump truly understands the current system for refugee intake. In Maine earlier this month, he warned that refugees to the United States are coming from the “most dangerous places,” an almost comical point: The very essence of a refugee is that she is coming from a place of danger. Refugees by definition do not come from stable, tolerant, liberal democracies.

Trump has also claimed, falsely or at the very least with great hyperbole, that there is “no system to vet” refugees from the Middle East. At other moments, he has simply said the system is bad: “There’s no way to properly vet these people, so what they do is make up paperwork.” There is a system in place, and it is exceedingly rare for refugees (and those who have been granted asylum in the U.S.) to commit acts of terrorism. The State Department told Fox News that about 12 out of 785,000 refugees admitted to the U.S. since 1975 have been deported or arrested thanks to security concerns that existed before they entered the U.S. Another minuscule fraction has become involved in terror later. But doubters say that it only takes one or two successful terrorists to produce carnage, and some critics, including my colleague David Frum, have deemed the system fraught.

What would Trump do to rectify the problem? His system of questionnaires, interviews, and background checks sounds broadly similar to the current system, which involved interviewing applicants, combing for worrisome connections, and checking their names against intelligence files. The inclusion of social media is somewhat fresher. The revelation, following the San Bernardino attacks, that U.S. screeners were not searching for applicants on social networks infuriated many conservatives. But that, too, has already changed, with the Department of Homeland Security scrambling to include those networks in their process.

Taken in sum, Trump’s ideas seem to have evolved from a clear-cut but arguably illegal process in the first place to a proposal that now largely resembles the status quo, although with a few additional, vague tests. What Trump calls “extreme vetting” looks quite a bit like the existing vetting, only with an adjective attached. If the past is any indication, however, Monday’s proposal may prove to be just another rough draft as well. Translation is an inexact and imperfect art.