(CNN) The unanimous vote among House Democrats to approve sweeping political overhaul legislation last week opened what is likely to be a sustained confrontation over access to the voting booth that could reshape not only the competition between the political parties but also the racial division of power in an irreversibly diversifying America.

The legislation, HR 1, has little prospect of becoming law anytime soon because Senate Majority Leader Mitch McConnell has already indicated he intends to block it from reaching a vote -- and President Donald Trump has committed to a veto if it somehow passes Congress.

But the bill identified a comprehensive agenda -- particularly in razing obstacles that discourage people from registering and voting -- that has quickly moved to the top of Democratic priority lists for the 2020 campaign and beyond.

And it makes clear that Democrats and civil rights groups are committed to a long-range campaign to leverage federal power to overcome state-level barriers, particularly across the Sun Belt, that local Republican parties have constructed, partly to delay the political emergence of growing minority communities, critics suspect, which tend to vote Democratic.

"There is a sense that while the restriction of voting rights and the closing of polling stations and the variety of things that have been disenfranchising younger voters of color, and younger voters in general, has been happening at a state level, it's been part of a national plan," notes sociologist Manuel Pastor, director of the Program for Environmental and Regional Equity at the University of Southern California. "So it's no surprise that once Democrats have control of the House they are trying to use the levers of the federal government to do something about this."

The HR 1 legislation offers political revisions on almost every front, from expanding public financing for federal elections to imposing new restrictions on lobbyists, requiring states to redraw congressional lines through an independent commission and mandating that presidential candidates disclose their taxes. But the bill's most consequential provisions would significantly expand access to voting and block many steps that states have taken to limit it.

"That's really the thinking behind a whole range of federal provisions here: to create the federal floor below which states can't drop," said Wendy Weiser, director of the Democracy Program at the Brennan Center for Justice at New York University law school.

Among other steps, the bill would require states to:

Automatically register adults to vote whenever they come in contact with government agencies

Allow same-day registration

Permit online registration

Limit the tools states have used to purge voter rolls

Provide at least 15 days of early voting opportunities

Eliminate barriers to voting by mail

Allow voters who don't have the identification required by state law to cast ballots if they present sworn affidavits

Weiser says these changes could increase the number of Americans registered to vote by as much as 50 million while outlawing many of the most controversial state barriers to registration and participation.

"There would be now a uniform way in which states would be uniformly registering everybody for whom they have reliable information as a citizen," she says. "That entire area will no longer be a tool to suppress votes."

Lopsided vote

In the vote last Friday approving the bill, HR 1 won support from all 234 House Democrats who voted, while every voting House Republican opposed it. That stark polarity underscores the extent to which access to the ballot box has grown into one of the most systemic conflicts between the two parties.

The confrontation has significantly escalated since the Supreme Court's 2013 Shelby County v. Holder decision . In that case, five justices appointed by Republican presidents outvoted four justices appointed by Democrats to overturn a key provision of the 1965 Voting Rights Act that required states with histories of discrimination to receive "preclearance" from the Justice Department before changing their voting systems.

Since then a procession of states, almost exclusively with Republican governors and legislatures, have narrowed access to voting. Under the umbrella of combating voter fraud, they have stiffened identification requirements to vote, restricted early voting, expanded "purges" of the voter rolls and added obstacles to registering voters.

In the past few years, several states under Democratic control have moved in the opposite direction, with a dozen now providing for some form of automatic registration for voters and several embracing other changes, such as voting by mail, meant to expand participation. When Democrats recently achieved unified control of the Legislature in New York state, for instance, one of their first actions was to p ass a broad package of voting revisions

warning that if HR 1 cleared the Senate, the President would veto it as a violation of "constitutional principles of separation of powers, federalism, and freedom of speech." The administration added: "H.R. 1 proposes to have the Federal Government micromanage elections that are largely and properly within the purview of the States themselves." The Trump administration, meanwhile, issued an official position warning that if HR 1 cleared the Senate, the President would veto it as a violation of "constitutional principles of separation of powers, federalism, and freedom of speech."The administration added"H.R. 1 proposes to have the Federal Government micromanage elections that are largely and properly within the purview of the States themselves."

This partisan divergence over voting marks a new dynamic, notes Scot Schraufnagel, a political scientist at Northern Illinois University who studies voting rules in the states. Until early in this century, he says, many of the states that made it easiest to vote were heavily rural Western states mostly under Republican control. "It's only the last two election cycles, 2012 and 2016, where Republican state party control correlates with (more difficulty) voting," Schraufnagel says.

The relationship is powerful now, however. In a recent paper, Schraufnagel and two colleagues ranked the 50 states based on ease of voting: Of the 20 states they identified as making it most difficult to vote, Trump carried 17. Hillary Clinton carried 12 of the 20 states where it is easiest to vote.

a similar change to ever pass legislation combating climate change. The 20 states where it is toughest to vote also have sent 30 Republican senators to Washington, who are likely to staunchly oppose any effort to overturn their states' rules. That suggests that any future legislative effort on voting rights may require Senate Democrats to consider ending the filibuster -- much as the "brown blockade" of Republican senators from energy-producing states might compela similar change to ever pass legislation combating climate change.

Collision over bill is revealing

The battle over voting access has become a critical front in the larger struggle over the nation's direction between what I have called the Democratic coalition of transformation -- centered on groups most comfortable with the demographic, cultural and economic changes remaking America -- and the Republican coalition of restoration, most uneasy about those changes.

Particularly in states across the Sun Belt -- from North Carolina, Florida and Georgia to Texas and Arizona -- the electoral competition is shaped by a stark demographic divide. In all of those states, Democrats are increasingly reliant on growing populations of younger and nonwhite voters. But in each of those states and others demographically similar to them, a Republican coalition almost entirely dependent on white voters -- especially older, blue-collar and non-urban whites -- still has the advantage, particularly in state elections.

In each state the Republican majorities have used that power to approve either restrictions on voting -- such as tougher voter identification laws -- partisan gerrymanders or both, making it more difficult for that emerging nonwhite electorate to overturn their dominance.

Thus the conundrum: Even as the minority populations grow in these states, the obstacles to voting extend the time before those populations can achieve enough political clout to tear down the laws that are delaying their emergence to begin with.

Though the minority population isn't growing there as fast, the same dynamic is present in Rust Belt states where Republican legislatures and governors empowered by the 2010 GOP landslide imposed new restrictions on voting or severely gerrymandered the lines for state elections, such as Wisconsin.

With HR 1 and a parallel push coming later in this Congress to restore the preclearance provision in the Voting Rights Act -- eliminated by the Shelby decision -- Democrats and civil rights groups are trying to outflank those state-level obstacles with renewed federal action. In that way, this focus reprises the logic of the Civil Rights Act of 1964 and the Voting Rights Act of 1965, which overthrew the regional barriers to equality across the South by setting new national rules.

"The 1960s were about breaking down an apartheid voting system in the South," says Pastor. "What we're seeing is an attempt to resurrect a system where certain kinds of people's voices don't become part of the policy process."

For both parties, the collision over HR 1 provides a revealing window into their broader direction. The increased emphasis on voter security and creating obstacles to voting in Republican-leaning states paralleled the party's broader strategic choice after the 2012 presidential election. Rather than seeking to expand its support among minority voters, as the famous Republican National Committee "autopsy" report recommended following Mitt Romney's defeat, the GOP turned more toward a message aimed at maximizing its support among whites uneasy about social change -- a shift symbolized by Trump's nomination and general election victory in 2016.

In mirror image, the striking Democratic unanimity over HR 1 underscores that all elements of the party now recognize how much their future may depend on mobilizing the increasingly diverse populations of younger Americans -- especially as so many older whites are drawn to Trump's confrontational message of racial nationalism.

Senate Democrats are developing a similar package. If Democrats win back the White House and unified control of Congress in 2020, "I could see it being the first piece of legislation," says Schraufnagel.

While McConnell and Trump can block federal action for now, the two parties' inimical incentives guarantee that the battle over federal action to expand voting rights is just beginning. As the nation inexorably grows more diverse, these conflicts, in fact, are far less likely to dissipate than to escalate.