Analysis by Ronald Brownstein

(CNN) -- With his threat to shut down the federal government unless he receives funding for his border wall, President Donald Trump is employing a tactic that is unpopular to advance a goal that may be even more unpopular.

Trump's threats -- and the muted public resistance to them from GOP congressional leaders -- offer the latest evidence that the party's drubbing in the midterm election has not changed the White House's fundamental strategic calculus.

Though the proposed border wall faces widespread opposition among all the groups in the electorate that powered the big Democratic gains in the House last month, and government shutdowns historically have alienated a broad range of the public, both the end and the means remain popular among the President's core supporters.

Trump may yet back down before triggering a government shutdown just in time for Christmas. But his determination to push this confrontation to the brink -- for a cause, building the wall, with such a narrow base of support -- underscores how committed he remains to energizing his base, even at the price of alienating the broader electorate.

Since Trump's snippy public meeting last week with likely incoming House Speaker Nancy Pelosi and Democratic Senate leader Chuck Schumer, most attention has focused on the President's willingness to accept responsibility for a possible government shutdown. That declaration flabbergasted many congressional Republicans, since previous shutdowns have always been unpopular and each party has maneuvered to pin blame on the other.

Public opposition to a shutdown over the wall

Uneasy GOP officeholders have legitimate reason for concern: In a National Public Radio/Marist survey last week, just 36% of Americans said Trump should shut down the government if Congress doesn't fund his wall. A 57% majority said he should compromise to avoid a shutdown.

But about two-thirds of self-identified Republicans in the survey said they would support a shutdown for the wall, and it is that core of immigration hardliners in the party that Trump has targeted with his agenda and rhetoric on the issue.

During the 2016 Republican presidential primaries, Trump's tough approach on immigration, symbolized by his calls for a wall across the southern border that he would compel Mexico to fund, was his distinguishing feature in the crowded field. Trump won largely by consolidating the portions of the GOP electorate most antagonistic to undocumented immigrants and immigration more broadly.

Exit polls in 20 states during the GOP primary asked if voters thought that undocumented immigrants should be allowed to obtain legal status or if they should be deported; in only two of the 20 states did a majority of voters even in the GOP primaries support deportation. Yet that hardline minority backed Trump in such overwhelming numbers that they provided a majority of his votes in 18 of the 20 states, the exit polls found.

But Trump's call for the wall has never won broad public support. For years, polls have consistently found that while Americans support a pathway to legal status or citizenship for undocumented immigrants without criminal records, they also place a high priority on ensuring border security. Yet even within that broad consensus, Trump's specific solution -- the border wall -- has always faced lopsided opposition.

In 10 Quinnipiac University national polls from April 2017 through August 2018, no more than 40% of Americans ever expressed support for the wall. Consistently, the share of Americans opposing construction of the wall has been much higher, from 57% to 64%. A CNN Poll conducted by SSRS that was released last week found 57% against a wall, compared with 38% in favor.

Opposition to the wall is overwhelming among all the groups that moved decisively away from Trump and the GOP in last month's election. In CNN's poll, Trump's border wall faced opposition from 76% of African-Americans, 66% of Latinos, 66% of adults younger than 35, 57% of independents, 66% of college-educated white voters and 56% of people aged 35 to 49.

Strong support for wall among Trump's base

Backing for the wall was centered firmly on Trump's core groups: In CNN's survey, the wall drew support from a robust majority of 78% of Republicans, as well as 49% of whites without college degrees.

But results from a survey earlier this year indicate the wall's base of support may be even narrower than those numbers suggest. When the nonpartisan Public Religion Research Institute asked about the wall in its annual American Values Survey, it found that two-thirds of white evangelical Christians supported building the wall. It also found that three-fifths of blue-collar white men who are not evangelical Christians supported the barrier.

But a solid 55% majority of blue-collar white women who are not evangelicals opposed the wall. And among whites with college degrees who are not evangelicals, the wall faced opposition from 63% of the men and 73% of the women.

Those attitudes about the wall closely track the voting patterns in last month's House elections, according to exit polls. As a new CNN analysis of the results showed, while Republicans in House races carried about three-fourths of white evangelical Christians and a narrow majority of the non-college white men who are not evangelicals, they lost each of those other groups. Among whites who are not evangelical Christians, Democrats won almost three-fifths of non-college women and college-educated men, and a head-turning 71% of the college-educated women.

Even before Trump's emergence, the Republican electoral coalition had grown increasingly reliant on the groups in American society that are most uneasy about demographic and cultural change in general and immigration in particular: that includes evangelical Christians, older, rural and many blue-collar whites. Simultaneously, Democrats have grown stronger among the groups most comfortable with the changes remaking America in the 21st century: younger, nonwhites, secular and college-educated white voters, especially women.

Trump's strategy

With his increasingly overt appeals to white racial resentments and conservative anxieties about other social changes such as the #metoo movement and increasing assertiveness of women in the workplace, Trump has intensified this re-sorting.

The 2018 election showed the risk of that process to the GOP, as the Democratic victories were propelled by enormous margins among the groups comfortable with change -- all of which are growing as a share of the society and electorate.

In the House, Democrats posted big gains in districts in diverse, information-age, economically thriving metropolitan areas almost everywhere: After November, Republicans hold only about 1 in 8 of the House seats where immigrants exceed their share of the national population, about 1 in 6 of those that are more racially diverse than the national average and about 1 in 4 of those with more college graduates than average.

In the Senate, the GOP lost seats in the diverse, younger, immigrant-heavy states of Arizona and Nevada. Even after Republicans gained a seat in Florida and held a seat in Texas -- another state with a large immigrant population -- Democrats now hold 33 of the 40 Senate seats in the 20 states where immigrants constitute the largest share of the population.

Several of the remaining GOP Senate seats in those immigrant-heavy states will start near the top of the Democrats' target list for 2020, including Colorado and Arizona, with North Carolina, Georgia and Texas presenting more difficult but not insurmountable challenges.

Few analysts in either party dispute that Trump's strategy of doubling down on the groups uneasy with change could allow him to squeeze out a narrow victory in 2020. But it has undeniably left the GOP in the situation of trying to extract greater advantage from groups that are shrinking -- a process that inexorably grows more precarious over time.

Triggering a government shutdown that most Americans oppose to advance the cause of building a wall that most Americans also oppose would stand, appropriately enough, as a monument to that high-risk strategy.