For the past decade, “comprehensive immigration reform” has meant primarily three things: (1) some type of amnesty program for illegal immigrants, (2) a mishmash of border-security measures aimed at curbing future illegal immigration, and (3) a massive increase in legal immigration, including a massive expansion of guest-worker programs.

While Congressional Republicans have blocked multiple efforts to pass such legislation — first under President Bush, and then again under President Obama — even many self-styled GOP border hawks have called for huge increases in legal immigration. Senator Ted Cruz, for example, proposed an amendment to the 2013 Gang of Eight bill that would have boosted the annual cap on H-1B visas (for tech workers) from 65,000 to 325,000 — a fivefold increase.

A few years later, of course, after watching Donald Trump surge to the front of the Republican presidential field, Cruz changed his tune: His November 2015 immigration plan advocated a 180-day suspension of the H-1B program, a thorough investigation of reported abuses, and a tightening of requirements. The Cruz plan also rejected any near-term increase in overall legal immigration. (“Under no circumstances,” it declared, “should legal immigration levels be adjusted upwards so long as work-force participation rates remain below historical averages.”)

Yet many other prominent Republicans still support much higher levels of legal immigration. A new Gallup survey confirms that most Americans — including overwhelming numbers of GOP voters — disagree with them.

Indeed, Gallup reports that more than three-quarters of U.S. adults believe immigration should be reduced (38 percent) or kept at its current level (38 percent), while only 21 percent believe it should be increased.

Among people who identify as or lean Republican, 60 percent want to reduce immigration, 27 percent want to maintain the present level, and only 11 percent want to increase it.

Among self-identified moderates, only 23 percent favor increasing immigration, versus 76 percent who favor reducing it (32 percent) or leaving it unchanged (44 percent).

Among Hispanics, 35 percent would prefer to reduce immigration; just 18 percent would prefer to increase it.

These figures remind us that there is a wide gap between elite and popular opinion on immigration. They also remind us that a serious immigration debate would go far beyond the issue of amnesty. Megan McArdle of Bloomberg View recently listed some of the questions policymakers should be asking:

How many people should we let in, of what education and skill level? How should we handle marital visas? What tradeoffs are we willing to make between national unity and the humanitarian and practical benefits of migration? . . .

Exactly what sort of country do we want to be? And what sort of new citizens do we want to recruit? The only path forward is to discuss those questions — frankly, with numbers.

Speaking of numbers, researchers Karen Zeigler and Steven Camarota of the Center for Immigration Studies estimate that immigrants and their minor children went from less than 7 percent of the U.S. population in 1970 to nearly 19 percent in 2015. Given the challenges America faces, there are legitimate economic, cultural, and security reasons to reduce immigration in general and low-skilled immigration in particular. By contrast, the arguments for increasing immigration — let alone massively increasing it — seem much weaker.

In any case, this is a crucially important debate that we need to have.