In the battle for control of both Congress and the White House, Republicans rely overwhelmingly on the places in the US that remain the least touched by immigration. Democrats depend primarily on the places with the most immigrants.

That contrast frames the inverse dynamic driving this volatile debate: generally it is the places with the least exposure to immigrants that are seeking to limit future migration, over the objections of the places with the most.

Even that paradox doesn't capture the full complexity of the conflict. At the federal level, Republicans led by President Donald Trump are now urging not only a crackdown on undocumented immigrants, but also the biggest reduction in legal immigration since the 1920s. But simultaneously, more local officials from both parties across the heartland are trying to attract immigrants they consider indispensable to their strategies for maintaining economic vitality and a critical mass of population.

"My sense is if you talk to local elected officials, policy makers, business owners, faith leaders, they get it -- they completely understand that immigration is what is going to keep them going," says Ali Noorani, executive director of the National Immigration Forum, and author of the book "There Goes The Neighborhood," which explores how communities across America are adapting to new arrivals. "But, especially in this day and age, for them to make that case publicly, when the other bullhorn is held by the President, is really, really hard."

Trump would trade protection for "Dreamers" for drastic cuts in legal immigration

Trump has disappointed some conservatives by indicating that he's willing to accept a pathway to citizenship -- albeit an elongated one -- for a substantial portion of the so-called "Dreamers," young people brought to the country illegally by their parents and previously protected by the Deferred Action for Childhood Arrivals (DACA) program. But he has infuriated Democrats and immigrant advocacy groups by tying any potential protection for the Dreamers not only to funding for a border wall and enhanced enforcement measures but also substantial reductions in legal immigration.

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In the proposal that Trump is expected to highlight in his State of the Union address Tuesday night, the administration has insisted that any deal for "Dreamers" include severe limits on immigration aimed at family reunification -- what conservatives call "chain migration." Trump wants to limit future legal immigration only to the spouses and minor children of American citizens and permanent legal residents. That shift could reduce legal immigration by as much as 40% over time, according to projections by the Migration Policy Institute . Hard-line legislation introduced by Rep. Bob Goodlatte of Virginia in the House would impose similar reductions on legal immigration , while Republican Sens. Tom Cotton of Arkansas and David Perdue of Georgia, in legislation Trump has endorsed, have proposed an even deeper cut of 50%. Any of these would represent the biggest reduction in legal immigration since the 1920s.

The voters most resistant to immigration

Both in the 2016 primaries and general election, Trump relied preponderantly on support from the voters most resistant to immigration. A majority of Republican voters supported building Trump's proposed border wall in just two of the 20 states where exit polls measured sentiment on the question in GOP primaries. Yet that minority of Republicans supported Trump in such overwhelming numbers that they provided a majority of the votes he received in 18 of the 20 states.

In the general election, the exit poll likewise found that just 41% of voters supported building the wall while a 54% majority opposed it. Yet once again Trump won such an overwhelming percentage among the minority that supported the wall (85% of whom voted for him) that they provided about three-fourths of all the votes he received, according to the exit poll.

The share of voters who believed that all undocumented immigrants in the US should be deported, as opposed to receiving legal status, was even smaller: just 25%, according to the exit poll. Yet once again they voted for Trump in such overwhelming numbers (more than four-in-five) that this relatively small group provided about 45% of his total votes.

A reliance on the places with the least exposure to immigration

Geographically the contrasts were equally pointed. In both Congress and the Electoral College, the GOP now relies predominantly on the places with the least exposure to immigration.

According to the Census Bureau's American Community Survey, in 2016 immigrants exceeded or equaled their 13.5% share of the national population in fourteen states. Trump won just three of them: Florida, Texas and Arizona. Hillary Clinton won the other 11, including eight of the top 10: California, New York, New Jersey, Hawaii, Nevada, Massachusetts, Maryland and Connecticut.

Overall, Clinton carried 16 of the 20 states where people born abroad constitute the largest share of the population. (Georgia was the only other state in the top 20 that Trump carried.)

Trump, in turn, dominated the places with fewer immigrants. He won 26 of the 30 states where immigrants constituted the smallest share of the population. (Minnesota, New Hampshire, Vermont and Maine were the only exceptions.) In 19 states, immigrants comprise only one-in-every-20 residents or less. Trump won all of them except for Vermont and Maine. The states on the very bottom of the list for immigrant presence represented some of Trump's strongest: West Virginia, Mississippi, Montana, Wyoming, North Dakota, Alabama, Kentucky and South Dakota.

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The same patterns persist in Congress. In the Senate, Democrats now hold 31 of the 40 seats from the 20 states with the highest share of immigrants. That number could increase after November's election: the Democrats' top two Senate targets are Republican-held seats in Nevada and Arizona, which are both among the nine the GOP controls in the high-immigration states. (Democrats have an outside chance at a third Republican senator on that list, Ted Cruz of Texas.)

By contrast, Republicans hold 42 of the 60 Senate seats in the 30 states with the smallest share of immigrants. And that number could rise as well after November. The GOP's top Senate targets this year are almost all Democrats from the low-immigration states, including Missouri, Indiana, North Dakota, Montana and West Virginia. (The one exception is high-immigrant Florida, where Republicans are optimistic that Gov. Rick Scott can oust Democrat Bill Nelson.)

In the House, the contrast is equally stark. Nearly 85% of House Republicans represent seats where the foreign-born share of the population lags below the national average. (In Goodlatte's seat, immigrants comprise only 5% of the population.) Over 60% of House Democrats represent seats where the foreign-born share of the population exceeds the national average. This divergence could widen as well in November. Many of the Democrats' top targets this year include suburban seats in major metropolitan areas with large immigrant populations, such as Orange County CA; Northern Virginia; Miami; and New Jersey.

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Democrats do better, and Republicans less well, in states with more immigrants partly because the GOP has struggled so much in recent years with all minority voters, whether native-born or immigrant. But many pollsters also say that unease about demographic change in general, and immigration in particular, often is also greater among whites in the places that are the least directly affected by it.

As the non-partisan Public Religion Research Institute reported in a nationwide study in 2016, "Notably, areas of the country that have been historical centers of immigration hold the most positive views of immigrants." The most negative attitudes were expressed in the Deep South, Appalachia and parts of the Plains and Mountain States -- areas with generally fewer immigrants.

A new focus on legal immigration

The demands from Trump and some GOP legislators in each chamber for cutbacks represent the GOP's first serious attempt to retrench legal immigration since 1996, after the 1994 landslide that swept the party to control of both congressional chambers for the first time in 40 years. That earlier push never generated much momentum: though the House Judiciary Committee approved cutbacks, one-third of House Republicans joined most Democrats to block them on the floor. Just 20 senators supported legal immigration reductions, with three-fourths of Republicans (including John McCain, Orrin Hatch and Mitch McConnell) voting no.

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This time, with Trump's vocal support, the effort may accumulate greater support. Yet with the exception of Perdue, few of the Republican senators from the high-immigration states have shown much enthusiasm for a crusade to reduce legal flows. (Late last week, Florida's Republican Sen. Marco Rubio, without directly criticizing the call for legal immigration reductions, pointedly suggested that any legislative package on DACA should be focused narrowly on closely related issues.)

And the push at the national level to reduce legal immigration collides with the increasing interest among local officials, even in many Republican-leaning heartland communities, in recruiting immigrants to stem population loss, particularly among people in the prime working years of 25-64.

The list of cities participating in the non-partisan Welcoming America network, which works with local governments and non-profits to promote the integration of immigrants, testifies to the breadth of interest in attracting new arrivals. The coalition includes not only Seattle and Los Angeles, Austin and Boston, New York and Chicago-big places with a long-standing immigrant heritage. It also encompasses heartland communities where Republicans typically run better than in the big metros: Akron, Toledo and Dayton, Indianapolis, Lincoln and St. Louis, Kalamazoo and Fargo, Nashville and tiny Clarkston, Georgia.

Noorani notes there is a "dissonance" between the push to attract immigrants in so many local communities, many of them Republican-leaning, and the escalating demands from national GOP leaders to roll back legal immigration. "It doesn't mean that what's happening locally is easy, but at the local level, if you've got a good mayor, a good city council, the police chief, the fire department, who are speaking to the values of immigrants to a particular community, that eases the tension," he says. "Right now, it's clearly not the President delivering that message."