(CNN) The 2020 election may test as never before one of the most enduring rules of presidential politics, the straightforward four-word maxim coined by Democratic strategist James Carville in 1992: "It's the economy, stupid."

Even amid record-low unemployment, robust economic growth and a roaring stock market, President Donald Trump has shown no signs of expanding his support beyond the roughly 46% of the vote that he carried in 2016.

National surveys now routinely find a huge falloff between the share of Americans satisfied with the economy and the percentage that approve of Trump's performance as President. And new academic research has concluded that attitudes about the economy were much less powerful in driving voters' decisions in 2016 and 2018 than their views about fundamental cultural and social changes, particularly race relations and shifting gender roles.

Each of these dynamics underscores how the economy's role in politics may be shifting as the basis of each party's political coalition has evolved. Increasingly, the parties are bound together less by class than by culture. As I've argued, the fundamental dividing line between the parties has become their contrasting attitudes toward the underlying demographic, cultural and economic changes remaking American society.

Democrats now rely primarily on what I've called the coalition of transformation, centered on the groups that mostly welcome these changes, particularly young people, minorities and college-educated white voters, all of them concentrated in major metropolitan areas. Republicans mobilize a competing coalition of restoration that revolves around the groups that are most uneasy about these changes: older, blue-collar, evangelical and rural whites.

Many political observers see clear evidence that attitudes toward these core questions of America's identity are overshadowing assessments of the economy in driving voters' decisions.

Brian Schaffner, a Tufts University political scientist, says a bad economy can still threaten a president and his party, as it did when the financial crash helped Barack Obama breeze to the presidency after President George W. Bush's two terms in 2008. But a good economy, he believes, may no longer be enough to dislodge the entrenched battle lines over these underlying cultural preferences.

"One thing you see in the two most recent presidencies, the Obama and Trump presidencies, is neither of them get much credit for good economies," Schaffner said in an interview. "They had different ceilings (of support), but they both had ceilings."

The trend was clear in 2018 elections

elections, when Democrats made their biggest inroads in white-collar suburban areas in major metropolitan areas that were almost universally succeeding economically: A CNN analysis found that The economy's diminishing impact was apparent in the 2018 midtermelections, when Democrats made their biggest inroads in white-collar suburban areas in major metropolitan areas that were almost universally succeeding economically: A CNN analysis found that the median income exceeded the national average in 35 of the 43 previously Republican-held House seats that Democrats won last November.

Exit polls found that Republican House candidates still carried an overwhelming share of the roughly 1 in 8 voters who described the economy as excellent last year. But among the half of 2018 voters who called the economy "good," GOP candidates eked out only a narrow 51% to 47% advantage, the exit polls found. In sharp contrast, Democrats carried almost exactly three-fourths of voters who described the economy as "good" in the 2014 midterms, while Obama held the White House.

On balance, any president, of course, would prefer to seek reelection with a stronger rather than weaker economy. Models from political scientists and academics that try to predict the outcome of presidential races typically place a heavy emphasis on measures of economic performance, such as growth in the overall domestic product or inflation-adjusted personal income. Most of those standard models now consistently identify Trump as a clear favorite for reelection

But Alan Abramowitz, an Emory University political scientist, says the effectiveness of models that stress economic performance to predict presidential elections may be eroding. "There's a possibility here, just based on what the survey data seems to show, that the connection between perceptions of the economy and opinions about the president has gotten weaker," he said in an interview.

Abramowitz's own forecast model -- which factors inflation-adjusted economic growth, incumbency and a president's approval rating -- puts Trump at about 50-50 odds for reelection. "There's a chance the economy is not going to play as big a role here," Abramowitz says.

Schaffner agrees. In a study of the 2016 election using data from the Cooperative Congressional Election Study, a large-scale pre- and post-election national survey, Schaffner and two co-authors found that economic satisfaction and dissatisfaction was much less important in predicting support for Trump or Democratic nominee Hillary Clinton than attitudes about race and gender relations . The more likely voters were to believe that racial discrimination is not a systemic problem and that women complaining about sexism were actually seeking unfair advantage over men, the more likely they were to support Trump. (That pattern was as powerful among women as it was among men.)

The relationship between those attitudes about fundamental cultural change -- particularly views about racism -- dwarfed assessments of the economy in predicting the vote, Schaffner said, even when accounting for the tendency of Democrats and Republicans alike to view the economy more positively when their party holds the White House.

Trump as force multiplier

Again using Cooperative Congressional Election Study data, Schaffner found that support for Republican and Democratic House candidates in 2018 correlated even more tightly than in 2016 with attitudes about the changing roles of women. A significant minority of Republican voters in 2016 who expressed sympathy for feminism, he found, switched to support Democrats last year. His research found that attitudes on whether racism is still a systemic problem also correlated even more closely with the House vote in 2018 than they had done two years earlier.

Those results partly reflect the long-term movement toward a political system that revolves more around cultural attitudes than class interests. But they also measure the extent to which Trump has thrust these questions of American identity to the forefront of political debate by identifying so unreservedly with the forces opposed to social change across a wide array of issues, from immigration to the protests of African American National Football League players to transgender rights and the appointment of socially conservative Supreme Court Justices Brett Kavanaugh and Neil Gorsuch.

Schaffner says Trump's emergence hasn't significantly changed the share of Americans who express positive or negative views about changing race relations or gender roles. Instead, Schaffner believes, Trump's impact has been to make those attitudes a more powerful force in determining which party voters identify with. Political scientists John Sides, Michael Tesler and Lynn Vavreck reached the same conclusion in their acclaimed recent book on the 2016 election, "Identity Crisis."

The reconfiguration of political allegiances around those views means that Republicans, under Trump, have been losing support from culturally liberal white-collar suburban voters who are thriving economically, even as they maintain solid advantages among socially conservative blue-collar and rural voters whose economic situation, while generally improving, remains much more tenuous overall.

Those contrasting trends have produced a striking divergence between attitudes about the economy and attitudes toward Trump.

In the most recent Quinnipiac University national survey , for instance, 76% of college-educated white voters termed the economy excellent or good. But only 36% of them said they approved of Trump's performance as President, and 59% said they definitely intended to vote against him for reelection.

Among younger adults, aged 18-34, 60% described the economy as excellent or good, but only 27% approved of Trump's performance and 63% said they definitely planned to vote against him in 2020. Among independents, 71% gave the economy good marks, but only 34% did the same for Trump's performance; just over half of them said they were committed to opposing him next time. Among Hispanics, two-thirds described the economy as strong, but less than a third approved of Trump's performance and almost two-thirds said they were committed to voting against him next year.

There was much less daylight between satisfaction with the economy and satisfaction with Trump among white voters without a college education, a group that has expressed more support for his cultural agenda. Among them, the falloff was much smaller between the share that said the economy was strong (77%) and the percentage that approved of his performance (55%); the share of those working-class whites who said they were committed to supporting Trump next year (46%) exceeded the share committed to opposing him (40%). The rest said they would consider voting for him.

Economy may just reinforce opinions on Trump

these college whites backed former Vice President Joe Biden over him by fully 2 to 1 in a putative 2020 match-up. Non-college whites in the state were almost exactly as positive about the economy, but 56% of them approved of Trump's performance and they gave him a nearly 20-point advantage over Biden. Quinnipiac discovered the same patterns in a recent poll in the pivotal state of Pennsylvania . Among college whites there, 81% described their personal financial situations as excellent or good and 73% said the same about the state economy. But only 35% of them said they approved of Trump's job performance, andthese college whites backed former Vice President Joe Biden over him by fully 2 to 1 in a putative 2020 match-up. Non-college whites in the state were almost exactly as positive about the economy, but 56% of them approved of Trump's performance and they gave him a nearly 20-point advantage over Biden.

Polls offer conflicting signals on how much Americans credit Trump with the good economic news.

Surveys consistently find that most voters are cool to his major policy initiatives. Polls have found that most Americans opposed his efforts to repeal the Affordable Care Act and that only a minority of Americans believe they have personally benefited from his tax plan; in the latest Quinnipiac survey, a plurality said his trade policies were bad for the economy.

But the share of Americans who say Trump deserves credit for the buoyant economy is rising in some surveys. Even that measure, though, seems influenced by the larger divide, with Republicans and the groups favorable to the GOP far more likely to credit Trump than those skeptical of him on other grounds.

For all these reasons, the strong economy seems more likely to reinforce than to recast the patterns of reaction to Trump's tumultuous presidency.

In the predominantly white, mostly nonmetropolitan places where voters are already drawn to Trump's confrontational cultural agenda, the economy may help him harden his support: Recent research by the Metropolitan Policy Program at the Brookings Institution found that the counties Trump carried in 2016 , most of them at the periphery of or beyond the major metropolitan areas, have added jobs at a much faster pace since he took office than they did under Obama.

But the diverse, younger, urbanized counties Clinton carried -- including almost all of the largest metropolitan areas -- are still adding jobs in larger absolute numbers than the Trump counties. And there's no indication that those gains are softening hostility to his social agenda and personal style.

"I would definitely think that who he's likely to lose (in 2020) are people who are doing fine economically but are just turned off by Kavanaugh and the immigration stuff, etc.," says Schaffner.

Abramowitz has similar expectations. "I think that where people come down on those cultural issues -- where they don't like what Trump is doing -- counts much more for them than the fact the economy is doing well," he said. "It's pretty easy to dismiss that or say that his policies are not responsible for it, that it's just a continuation of the recovery" under Obama.

In his meteoric political career, Trump has upended a succession of political rules and truisms. The next one may be views about the economy's primacy in determining the outcome of presidential elections.

That assumption was already eroding before Trump emerged, but if next year's election divides the country along the same lines that have shaped his presidency, political experts may settle on a new four-word maxim: "It's the values, stupid."