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Preparing once more to celebrate the shared beliefs that unite their nation, lots of Americans seem to be struggling to keep track of what those are.

One vivid measurement of modern America's turbulent cultural politics was recorded this past winter, in the postelection congressional vote enacting the Respect for Marriage Act.

The RFMA legislation confirmed and codified the nationwide legalization of same-sex marriage that had been ordained by the Supreme Court in 2015, but which some progressives feared was endangered after the high court overturned abortion rights last year. The new law also formally repudiated an earlier, directly contrary federal law — the Defense of Marriage Act. DOMA had been enacted 26 years earlier, in 1996, essentially to block the advance of same-sex marriage.

One sign of the striking change in American social attitudes over that quarter century was visible among Republicans. In 1996, GOP House members had voted 224-1 for DOMA — that is, against accommodating same-sex marriage. Republicans in the Senate concurred 54-0.

By 2022, Republicans opposed same-sex marriage (voting "no" on the new RFMA law) only by 157-47 in the House and 36-12 in the Senate — still strongly disapproving, but no longer unanimous.

The Democratic transformation was altogether more complete. In 1996, 64% of House Democrats and 70% of Senate Democrats had distanced themselves from same-sex marriage, voting for DOMA.

Last winter, not a single Democrat in either chamber voted against the new law affirming gay unions.

So while the GOP position on same-sex marriage changed in 26 years from all-but-unanimous opposition to merely decisive opposition, Democrats journeyed all the way from decisive opposition to unanimous endorsement.

These gymnastics describe much of the polarizing turmoil in U.S. politics today. In a recent review of decades of data from the NBC News/Wall Street Journal Poll, Bill McInturff of Public Opinion Strategies describes as the "most stable finding" a tendency for Republicans to "barely budge on a host of issues while Democrats' positions ... have fundamentally shifted."

It's possible to overstate the case. GOP hostility to affirmative action (culminating in last week's Supreme Court ruling against it) and gun control has grown sharply over three decades, while Democratic support for those policies, which was already high 30 years ago, has increased only modestly.

But on a good many other issues, these poll numbers indeed show Republicans changing little, or even drifting in a progressive direction, while Democrats lurched sharply to the left and largely banished dissent from their ranks.

The percentage of Republicans who believe government should "do more to help meet the needs of people" rose from 17% in 1995 to 23% in 2021. Among Democrats, the figure jumped from 45% to 82%.

In 2005, 37% of Republicans said "immigration strengthens the U.S." By 2019, 44% did. Democrats' confidence in the benefits of immigration soared from 45% to 81% in the same period.

Attitudes about abortion hardly changed among Republicans (or independents) between 2008 and 2023 (Republicans saying the procedure should be legal in most or all circumstances rose from 25% to 28%). Among Democrats diversity of opinion all but vanished, with support increasing from 68% to 89%.

And so it goes. Not that Minnesotans need national poll data to see this basic pattern. It is certainly true that since the days of Dave Durenberger and Al Quie, Minnesota Republicans have grown more conservative. But the transformation of the DFL, particularly on social issues, has been even more sweeping and ambitious.

Take Gov. Tim Walz. As a six-term congressman from the bucolic First District, Walz was what might be called moderately moderate, routinely scored among the more centrist Democrats in the U.S. House. He told MinnPost as recently as 2016: "You cannot run in this district ... being on the far left of the Democratic Party ... . [M]ost people live within the 30 yard lines. They expect me to represent that ideology."

Walz has wandered a ways from midfield since. Elected governor in 2018 touting a "One Minnesota" agenda, he signed something more like a "Won Minnesota" agenda into law in this year's session, from limitless abortion and the full-spectrum gender identity agenda to ballooning state spending, marijuana legalization, votes for felons, etc., etc. Walz has become something of a progressive paladin, boasting of Minnesota as "an island of decency ... of sanity" standing against "a march ... of bigotry and hatred" in less enlightened states.

There's an impressive sincerity — an authenticity, to use a favored word — in the militancy of today's American left, a willingness to enact what they preach that conservatives seldom match when they have power, perhaps because conservatives in the end don't want government to transform society. (Right-wing populists may be another matter.)

Anyway, whether one celebrates it or laments it, progressives' great leap leftward appears to be one of the central forces driving Americans apart. The question is whether it will go too far — as do, eventually, most political pendulum swings — and if so what form a reversal would take.

A few clues are visible. As part of its annual Values and Beliefs poll, released last month, the Gallup organization reported a notable decline in the percentage of Americans saying "gay or lesbian relations are morally acceptable." It wasn't the first dip in approval levels during the remarkable two-decade rise in acceptance of same-sex relations, but it was comparatively large, from 71% approval overall to 64%. Republicans' acceptance dropped especially sharply, from 56% a year ago to 41%. But even among Democrats approval fell from 85% to 79%.

That America's swift and sweeping embrace of equal rights for sexual minorities may have hit an obstacle was also suggested by news analyses reporting that this year's Pride celebrations took place amid "a troubling year for LGBTQ people and allies" particularly in light of legislation in numerous states restricting gender-affirming care for minors, school curricula focused on sexuality, transgender participation in girls and women's sports and more.

With the transgender rights agenda, could American progressives be demanding one transformation too many from society? It's an agenda that in some forms seems to demand, not merely live-and-let-live equality, but that all Americans embrace a profoundly altered understanding of one of life's fundamental realities — and teach it to their children.

Andrew Sullivan, self-described "marriage equality pioneer" turned "total pariah among the gays" argues in a recent blog post that the "far left" has "reignited homophobia" through an "illiberal" campaign in some quarters to use "public education, corporate power and government fiat to enforce the postmodern doctrines of queer and gender theory ... ."

Sullivan writes that it's no surprise "we've seen a reaction" because "When majorities supported gay couples getting married, they did not thereby support having their daughters forced to shower next to biological males in locker rooms, or compete with them in competitive sports; they did not support teaching kindergartners that their bodies have nothing to do with whether they are boys or girls; they did not support using unapproved drugs on troubled children to arrest their puberty ... ."

America has settled, compromised and papered over some deep divisions in its storied past. But we have our work cut out for us once more.