In a book released on the eve of the 2016 election called “Asymmetric Politics,” political scientists Matthew Grossmann and David Hopkins argued that America’s political parties don’t just have different ideologies, but are really different kinds of organizations. “Republicans are organized around broad symbolic principles, whereas Democrats are a coalition of social groups with particular policy concerns,” the authors concluded.

I don’t want to treat that book as gospel, but it speaks to a certain understanding that has existed throughout my 17 years covering national politics. Democrats have been considered the party of Asian, black, gay, Jewish and Latino people, along with atheists, teachers, union members, etc. — in short, a coalition organized around a bunch of different identity groups. Meanwhile, Republicans have been thought of as the party of small government, low taxes, a strong national defense and “traditional” moral values — in short, a coalition based around a few core ideological principles.

That has always been a fairly simplistic view of the parties. (And Grossmann and Hopkins’s book is much more nuanced.) But as an easy rubric to understand the two parties it worked. It still does, to some extent. But less and less so.

The two big stories happening right now in American politics — the 2020 Democratic primary and impeachment — show both parties being reshaped in ways that break with that asymmetry: The GOP is becoming increasingly organized around identity groups, and Democrats are becoming increasingly ideological.

Let me start with the Republicans.

With Republicans on Capitol Hill strongly defending President Trump amid the Ukraine scandal, you might say that the GOP has simply abandoned many of its principles in deference to Trump. Maybe. But I think the more accurate story is that Republicans on Capitol Hill are standing firmly behind Trump because GOP voters and GOP activists and elites are demanding that they do so. There just isn’t much room to break with the president of your party if close to 90 percent of voters in the party approve of him and many of those voters get their news from sources strongly supportive of that president.

Why are Republican voters and elites so strongly aligned with Trump? There’s not a simple answer, but I think identity — rather than ideology — is a big part of it. Trump is defending the identities of people who align themselves with the GOP, and this is a more powerful connection and reason to back him than pure ideological concerns. In defending Trump, conservative voters are really defending themselves.

No party ever governs strictly on ideology, but some of the breaks with conservative orthodoxy in the Trump era are notable.

If you think of the GOP as being broadly wary of government intervention into the economy, it’s been striking to watch the Trump administration try very hard to prop up the coal industry — even as the rise of natural gas and other alternative fuel sources have reduced the need for coal. The administration’s limits on travel from certain countries and cuts in the number of refugees who are entering the U.S. have affected Muslims most, suggesting that the GOP’s long-championing of religious freedom is now really just about defending the values of Christian and Jewish people. On trade policy, Trump imposed tariffs on China and other nations, and after those nations retaliated by making it harder for U.S. farmers to sell their goods abroad, the administration gave direct financial aid to farmers.

The Republican Party has traditionally favored few tariffs, limited government intervention in the economy and not giving government money directly to people in lieu of them earning it through work. Its recent actions seem out of character for a party organized around a particular ideology.

But if you think of the GOP as being organized around identity groups, these policies hang together quite well. The clear beneficiaries of the Trump administration’s actions have been businesses and corporations whose leaders back the president (such as those in the coal industry), conservative Christians, farmers, gun rights enthusiasts, people wary of increases in the number of foreign-born Americans and Islam, people wary of movements like Black Lives Matter and MeToo, pro-Israel activists and residents of rural areas.

Of course, I’m not the first person to notice any of this. The journalist Ron Brownstein refers to the GOP as the “coalition of restoration,” trying to fight against a “coalition of transformation” led by Democrats. Robert Jones, head of the Public Religion Research Institute, has described Trump as the defender of a “white Christian America” that sees itself in decline. In a recent speech, Attorney General Willam Barr praised the “Judeo-Christian values that have made this country great” and warned that “irreligion and secular values are being forced on people of faith.” All three of those formulations describe a complicated mix of identity and ideology.

“Some values and preferences that were always there, like racial resentment, rural resentment, nationalism, are being amplified and others, like free markets, are being diminished,” Hans Noel, a scholar on political parties who teaches at Georgetown University, told me.

“Allegiance to Trump is becoming more important to what it means to be conservative,” he added, “But post-Trump, that change may persist, with a conservatism that is more populist and nationalist.”

You might argue that this was always the Republican Party — that the GOP of Ronald Reagan and the two Bush presidents was similarly organized around conservative identity groups and not ideology. Perhaps the Bushes downplayed that dynamic for electoral reasons and to be “politically correct,” and therefore presented themselves as, say, more liberal on racial issues than the party’s base voters really wanted. Maybe Trump has simply stripped away the artifice. And you could certainly also argue that the Trump administration, particularly its aggressive push to reduce the number of people on Medicaid, is quite ideologically conservative on many issues.

Notably, Hopkins mostly disagrees with me, arguing that there have been some shifts in the Trump era but that the GOP has not fundamentally changed.

“His racial appeals are more common, more central and more overt, and he is more likely than most Republicans to simply be misleading or dishonest about what his policies are,” he told me. “But his appeals to patriotism, nationalism and nostalgia for an idealized past are very much in line with traditional conservative rhetoric, and he increasingly speaks the language of small government and capitalism.”

I think those arguments have merit. I don’t think that the Republican Party has abandoned ideology in favor of identity completely. But it does seem like identity is playing a bigger and clearer role than it did a decade ago.

Let’s move to the Democrats. Polling shows that a rising number of Democrats view themselves as liberal — now half of the party, compared to less than a third in the early 2000s. Democratic voters are increasingly likely to support liberal positions such as allowing more immigrants into the country and the government playing a role in helping Americans pay for their health care.

But the shift among Democrats is even more evident among activists and elites. Groups like Black Lives Matter, Demand Justice, the Sunrise Movement, Planned Parenthood and the newly-revived Poor People’s Campaign are pushing the Democratic Party in a more ideological direction. That ideology is perhaps best defined by a push for equality across a lot of realms — and particularly around ethnicity and race, gender, income, sexual orientation and wealth.

I think this is why Kamala Harris struggled to win the support of young, liberal black Democratic activists in her presidential run. She often tried to connect with them on identity (as a woman of color), but many of them were more interested in Bernie Sanders and Elizabeth Warren, who both made taking strong stands on racial and wealth inequality central to their candidacies.

“What makes the Green New Deal notable is that it’s a solution to climate change on explicitly social-democratic grounds,” said Daniel Schlozman, an expert on parties who teaches at Johns Hopkins University. He was referring to the fact that the Green New Deal is an environmental proposal but also includes liberal goals like guaranteeing all Americans a job and the ability to join a labor union.

I don’t want to overstate this shift, which I think is largely about party activists and a certain bloc of the party’s elected officials, including Sanders and Warren. You might argue both that Democrats have long been obsessed with equality and that the party still functions effectively as a bunch of different groups joined together. And it’s worth noting that about half of Democratic voters identify as “moderate” or “conservative,” not “liberal.” Another reason to be cautious about the idea that Democrats are more ideological than ever is that the leader in the national polls in the Democratic primary, Joe Biden, is running much more as a coalition-style candidate than an ideologically driven one. He seems to be trying to capture the nomination by combining the support of blacks, Catholics, liberals, moderates, Latinos, union members and whites, as opposed to running as an explicitly moderate or liberal candidate.

“I think there’s a ways yet to go before the trends we see add up to a fundamentally ideological Democratic Party,” said Hopkins. But he added, “Sanders and Warren are trying to redefine the party, and there’s a chance they or their political descendants could succeed in the future.”

Indeed, I think the party is changing, even if it has not fully changed. There has been a huge shift over the last five years by the Democratic Party’s officials, activists and even its voters in terms of viewing racial inequality as being principally about societal problems like racism (rather than shortcomings in effort by black people). A greater focus on gender equality in the party has forced Democrats like Biden to cast aside support for limits on abortions that some of these pols had embraced in the past. Biden often criticizes the rising left wing in his party, but the former vice president’s actual campaign positions are solidly liberal — he’s against the death penalty, and supports allowing federal funding to be used for abortions, expanding Medicare to many more Americans, free community college, and decriminalizing marijuana. In many ways, Biden (and Pete Buttigieg) are essentially conceding to the rising power of the ideological left and simply offering a milder version of its ideas than Sanders and Warren.

Why do these party changes matter? First, they explain why fights between the elites and activists within both parties are so intense. Never-Trump Republicans such as Bill Kristol deeply believe they are defending the true Republican Party. Old-style Democrats such as Biden think they are defending the true Democratic Party. Secondly, these shifts explain why some seemingly-on-the rise politicians are struggling. Former House Speaker Paul Ryan was trying to find some middle course between the more ideologically conservative old-style GOP and the more identity-driven Trump version and just couldn’t. I think Harris tried both to connect with the rising activists in her party and the more traditional folks and managed to excite neither group.

Third, and perhaps most importantly, these shifts matter because America is to some extent in a partisan civil war, and we essentially have three competing views on how to end it: A Biden/Bush/Kristol style approach that downplays divisions among America’s various identity groups and reaches for more compromises; a Sanders/Warren approach of resetting America along more equal lines; and a Trump/Barr vision that is decidedly Judeo-Christian and favors maintaining traditional norms over upsetting them to expand equality.