(CNN) The House of Representatives this week is poised to pass its most significant gun control legislation since President Bill Clinton's first term -- and in the process highlight a fundamental transformation in the Democratic Party's center of gravity.

The proposal has little chance of becoming law with a Republican-controlled Senate. But the impending passage of a bill to impose universal background checks on all gun purchases, which is scheduled to reach the floor Wednesday, will mark the first time the House has cleared a major gun control bill since August 1994, when it approved a ban on assault weapons as part of a comprehensive crime bill. And while 77 House Democrats -- predominantly from rural, blue-collar and Southern districts -- opposed the assault ban in 1994, advocates expect that Democratic defections on the background check bill may not reach double digits.

"I do expect Democrats will be united," said Democratic Rep. Ted Deutch of Florida, chief whip for the House Democrats' Gun Violence Prevention Task Force.

The convergence of Democrats around the universal background check bill partly derives from the overwhelming public backing for the measure, which usually exceeds 80% support in polls . (The bill would close what's called "the gun show loophole" by including such venues, which are now exempt, in the requirement for background checks on all guns sold through licensed dealers.) But the Democratic consensus also reflects a larger shift in the party whose implications extend far beyond issues relating to guns.

Compared with the 1990s or even the early 2000s, House Democrats today are far less dependent on districts with large numbers of culturally conservative blue-collar and rural voters. Instead, the party's new majority is centered on urban and suburban districts that are either racially diverse, well educated, or both.

The willingness, even eagerness, of most House Democrats to embrace new gun control measures highlights how the party's evolution into a metropolitan-based coalition is shifting its incentives -- and reconfiguring its central fault line. For years, social and cultural issues -- ranging from abortion, gay rights and guns to questions of racial equity and immigration -- created the most difficult divisions for a Democratic House caucus trying to protect a large number of rural and Southern seats.

But those social issues are likely to prove much less divisive for today's metro-centered party. The big vote expected Wednesday for the background check bill will likely be only the forerunner for aggressive House action in the months ahead on an array of other hot-button cultural issues that once divided the party -- from providing legal status to undocumented immigrants brought to the country as children by their parents to expanding protections at work for gays and other measures to restrict access to guns, for instance by raising the minimum age to purchase one.

"I think we are going to see a consistent and sustained legislating on gun safety," said Peter Ambler, executive director of Giffords, the gun control group formed by former Rep. Gabby Giffords. "Guns used to be an issue that divides Democrats and unites Republicans. Now the opposite is true."

Moving forward, this reconfigured House Democratic caucus is likely to fracture more around issues relating to taxes, spending and the role of government. The new fissure may involve lawmakers from affluent suburban districts resisting the most ambitious spending plans of their liberal colleagues from more safely Democratic areas, such as single-payer health care.

"The fault lines are now around 'Medicare-for-all,' and free college and guaranteed federal jobs and the kind of things that were in the talking points that went with the Green New Deal," notes Matt Bennett, executive vice president for public affairs at the centrist Democratic group Third Way.

While those disputes may be approaching, Wednesday's gun vote will reveal a degree of consensus among Democrats on social issues unimaginable in earlier decades.

When Clinton passed his gun control bills during the early 1990s, he faced widespread opposition from House Democrats representing rural and blue-collar districts. In 1993, 69 House Democrats -- over one-fourth of those who voted -- opposed the Brady bill requiring background checks for all gun sales from licensed dealers. The 77 House Democrats who opposed the assault weapon ban in 1994 represented fully 30% of those voting. (Both measures passed only because of substantial crossover support from Republicans representing suburban districts outside the South.)

In the 1994 midterm elections, two months after Congress approved the assault weapons ban, Republicans surged to control of both the House and Senate, and particularly devastated Democrats across the South. Though the Republican wave swept out even many House Democrats who opposed Clinton's gun control agenda, those losses discouraged the party from pressing further gun control initiatives. And when Democrat Al Gore narrowly lost the 2000 presidential election, in part because he failed in heavily blue-collar states where the National Rifle Association campaigned fiercely against him (including New Hampshire and his home state of Tennessee), the conviction hardened among most Democrats that gun control had become a losing issue for the party. After losing the House in 1994, Democrats controlled the chamber for just four years before seizing it again in the 2018 election.

As the party's presidential nominee, John Kerry downplayed the issue in 2004 (even being photographed on a goose hunt) and President Barack Obama almost completely avoided it in both his 2008 and 2012 campaigns. In 2009 and 2010, while Democrats held unified control of government, they did not advance any major gun control proposals.

"I don't remember anybody even suggesting that we ought to do guns back then," said Ambler, an aide at the powerful House Rules Committee at the time. "It was off the table."

Even as late as 2011, 43 House Democrats voted for NRA-backed legislation that would override state limits on carrying weapons by requiring every state to honor a concealed carry permit granted by any other state.

But after Obama's re-election in 2012, two factors pushed Democrats to reconsider. One was the trauma of continued mass shootings, starting with Sandy Hook and continuing with a litany of tragedies so searing they are known by just their locations: Charleston, the Pulse nightclub, Las Vegas, Parkland.

The other factor was a growing awareness that the voters they feared most to alienate by advancing gun control measures -- particularly blue-collar and rural whites, especially men -- were already abandoning the party over other issues. Meanwhile, stronger measures to control guns consistently drew majority support in polls from the constituencies that the party increasingly relied on, particularly minorities, suburbanites and well-educated whites, especially women.

Over time, the evidence grew more irrefutable that by abandoning gun control, Democrats were trying to placate voters they had already lost , while slighting the voters they were attracting. In the latest polling from the nonpartisan Pew Research Center, for instance, two-thirds of nonwhite adults, nearly two-thirds of college-educated white women and a majority of college-educated white men all said it was more important to control gun ownership than to protect gun rights --while a nearly two-thirds majority of blue-collar white men and a thin plurality of blue-collar white women said the opposite.

The current among Democratic officials started to shift when Obama pushed a universal background check bill after Sandy Hook. Fifty Senate Democrats (including two independents who caucused with the party) voted for it in 2013, and only five voted no, one of whom, Senate Majority Leader Harry Reid, did so only for procedural reasons. (The bill failed to reach the 60 votes required to overcome a Republican filibuster, and the House, under GOP control at the time, refused to consider it.)

By 2016, Hillary Clinton advanced a more aggressive gun control agenda than any party presidential nominee since Gore in 2000. In 2017, the number of House Democrats who supported the NRA-backed legislation on nationwide concealed carry permits plummeted to six. And in 2018, dozens of Democratic challengers in House races touted their support for additional gun control measures, particularly the universal background checks. On Election Day, 40 Democratic challengers beat Republican incumbents with strong records of supporting the NRA, according to Giffords' calculations.

"Forty Democrats were elected to replace Republicans and almost every one of them made gun safety an issue in their campaign," said Deutch.

The key to the shifting politics of guns is that Democrats from such suburban seats in all parts of the country -- even the South -- are generally supporting tougher restrictions. Rep. Lucy McBath, an African-American Democrat, beat a Republican incumbent in suburban Atlanta by stressing her support for gun control. The Giffords organization closed its election campaign last fall with heavy spending that helped Democrat Lizzie Fletcher oust Republican Rep. John Culberson in the suburbs of Houston.

"If I told you I couple of years ago that we'd close doing that, you'd tell me I shouldn't have the keys to a political program," Ambler said. "We made guns part of the message that got him fired."

While the "blue dogs" centered in rural districts provided the core internal Democratic resistance to gun control in earlier years, advocates are confident the universal background check bill will draw support from almost all of today's largely suburban blue dog caucus, starting with its chair, Rep. Stephanie Murphy, an Asian-American and strong gun control advocate who represents a seat outside Orlando. Although the blue dogs will likely resist the left's most expansive plans for taxing and spending, most of them comfortably embrace the party's liberal mainstream on cultural issues.

Today's blue dogs "don't look anything like ... the guys who were voting against those things under Clinton," said Bennett. "The most avowedly conservative of the Democrats, the centrists, even most of them are going to be on board for these (social) things."

Ambler anticipates that more Republicans will cross over to support the background check bill than Democrats will defect to oppose it. And both Ambler and Deutch consider it likely that House Democrats will pass other gun-related legislation over the next two years, such as measures to raise the minimum age for gun purchases to 21; "red flag" laws designed to make it easier for law enforcement to confiscate guns from individuals considered an "extreme risk" of violence; and possibly legislation to ban certain types of semiautomatic assault weapons and high-capacity ammunition magazines.

Deutch has introduced legislation to regulate assault weapons under the National Firearms Act, which bans fully automatic weapons. "We are going to have a debate on weapons of war and whether they belong in our community or not," Deutch says.

Any gun control measure the House approves, of course, still faces very long odds in the Senate, which is controlled by a Republican majority rooted in rural states, where gun ownership is more prevalent and the NRA is strong. But even so, a strong House vote to approve universal background checks on Wednesday would mark a milestone in the Democrats' reconfiguration into a party advancing the cultural priorities of metropolitan America.

Simultaneously, the predominant opposition to the bill expected among House Republicans will underline the GOP's identity as the voice primarily of voters beyond the biggest population centers. (President Trump on Monday already warned that he will veto the bill if it clears both chambers.)

In that way, the Democrats' new unity on guns -- and likely on other social issues -- seems certain to reinforce and even accelerate the geographic and demographic resorting of the parties that has remade American politics since the House last approved a major gun control bill almost 25 years ago.