Nate Cohn for NYT’s The Upshot:

When Barack Obama won re-election in 2012, it seemed to mark the beginning of a new era of Democratic dominance, one propelled by the rise of a new generation of young, secular and nonwhite voters.

With hindsight, the 2012 election looks more like the end of an era: the final triumph of the social movements of the 1960s over the once-dominant Reagan Republicans.

Instead, it’s the three Trump elections — in 2016, 2020 and 2024 — that look as if they have the makings of a new era of politics, one defined by Donald J. Trump’s brand of conservative populism.

Whether you call it a realignment or not, American politics hasn’t been the same since Mr. Trump won his party’s nomination. The two parties clash over areas of former consensus, even as they reach détente on issues that defined the polarizing 2004 and 2012 elections. It can be disorienting for anyone who came of age before Mr. Trump. It can even feel like American politics has been turned upside down.

ntil Mr. Trump, there was a lot about American politics that you could take for granted. The meaning of the two parties seemed clear. Republicans represented Reagan’s three-legged stool of small-government fiscal conservatism, the religious right and foreign policy hawks. Democrats represented the working class, change and the causes of liberal activists.

Every four years, the two parties mostly litigated the same fights over the same issues. They rehashed arguments over war and diplomacy; entitlement spending and tax cuts; “family values” and the social movements of the 1960s; or trade and free enterprise versus labor and protecting jobs. It led to predictable demographic divides and recurring, long-term electoral trends.

That all changed when Mr. Trump came down the escalator. On some issues, it can even seem as if the parties have switched places. Today, Mr. Trump champions the working class, rails against elites, strives to protect American jobs and criticizes traditional U.S. foreign policy, all while Democrats defend the establishment, norms and the old foreign policy consensus.

Longstanding areas of bipartisan consensus have suddenly become fiercely contested. Immigration, free trade, America’s postwar alliances and even America’s support for democracy at home and abroad have all become defining conflicts between the two parties during the Trump era, rather than areas of agreement. Yet at the same time, the two parties seem to have reached a truce on the most bitter fights of the Bush-Obama era, like the war in Iraq, Social Security and same-sex marriage.

Much of the Republican Party’s old establishment — like the Cheneys, the Romneys, Paul Ryan — is now without a home. At the same time, many former Obama supporters, from Robert F. Kennedy Jr. to Elon Musk, suddenly find themselves near the center of Trump world….