A huge amount has already been written about the GOP’s over-reliance on aging downscale white voters, and what this means for the future of the two parties. For instance, Ron Brownstein has long argued that the Democratic Party’s increasing dependence on the “coalition of the ascendant” — young voters, minorities, and college-educated whites, particularly women — has meant that Dems are reorienting their priorities in a way that no longer ministers closely to the the preoccupations of non-college whites, who are declining as a share of the vote.

That, in turn, has set in motion an argument over whether Republicans are taking a great political risk in failing to reform the party’s policy agenda to appeal to those growing consistencies.

In a terrific piece, political scientist Alan Abramowitz frames this debate in even starker terms, noting that not only is this trend likely to continue; Republicans may be doomed to perpetuating it:

Today, the Republican electoral coalition remains overwhelmingly white. Nonwhites made up only 10 percent of Romney voters according to the 2012 national exit poll. But the nonwhite share of Democratic voters has increased fairly steadily since the 1960s and that trend has accelerated since 1992. Nonwhites comprised 45 percent of all Obama voters in 2012, and a majority of Obama voters under age 40.

The political significance of increasing racial diversity reflects the reality that, despite much progress in race relations over the past half century, American society remains deeply divided along racial lines. In many ways, the United States is still a segregated and unequal society. African Americans and Latinos continue to experience significantly worse health outcomes, poorer educational and job opportunities, inferior housing, higher unemployment and lower incomes than white Americans…These differences in life experiences and opportunities are reflected in sharply differing views on issues such as taxation, spending on social services and the proper role of government — as well as major differences in party identification and voting behavior.

The growing dependence of Democratic candidates and office-holders on nonwhite voters, along with a Republican strategy of appealing to white voters unhappy with the Democratic Party’s racial and economic liberalism, has contributed to an ideological and regional realignment within the white electorate. Conservative whites in the South and elsewhere have moved increasingly into the Republican camp, while moderate-to-liberal whites in the Northeast, Midwest, and Pacific states have moved increasingly into the Democratic camp.

There is every reason to expect these trends will continue. Census data indicate that the nonwhite share of newly eligible voters will continue to grow for many years. Yet despite the threat that this trend poses to the future viability of the Republican Party in national elections, the influence of the ultra-conservative, anti-immigration tea party movement makes it unlikely that the GOP will be able to successfully appeal to this growing nonwhite electorate. As a result, the racial divide between the parties’ electoral coalitions is likely to increase over the next several election cycles.

I’m not one who thinks that current demographic trends portend a certain electoral realignment that will all but put the presidency out of reach for Republicans in 2016. In their book on the 2012 election, John Sides and Lynn Vavreck detail a host of reasons why such predictions very well may not pan out.

That said, analyses like these from Abramowitz underscore yet again just how large a gamble Republicans are taking by failing to moderate on issues from immigration to gay rights, and by remaining wedded to a Tea Party worldview “in which virtually every reference to government is negative, disparaging, and denigrating,” as Michael Gerson and Peter Wehner put it. As they note, many of today’s Republicans, for reasons rooted in short term political expediency, have invested an enormous amount in the idea that the Obama agenda represents a frighteningly radical and destructive break with the country’s founding values — a threat to American freedom itself – an unhinged assessment that has left no room for them to articulate a “positive governing vision.” Yet as Abramowitz points out, growing segments of the electorate want government to play an activist, interventionist role.

To focus on immigration reform in particular, some conservatives have pointed to this basic disagreement with Republicans over government and asked: If these groups disagree with us on core ideological questions, why would immigration reform help matters? It’s a good question. But the counter-argument is that embracing immigration reform could at least lead some of these constituencies to give Republicans a hearing on other big questions. Not acting on immigration seems like it will only compound the gamble. And if Abramowitz is right about where current trends are heading, it’s an epic gamble indeed.

Greg Sargent writes The Plum Line blog, a reported opinion blog with a liberal slant -- what you might call “opinionated reporting” from the left.