William Voegeli, in an article for the Claremont Review called "The Wilderness Years Begin," cites an article by Ronald Brownstein.
Start by considering the electorate's six broadest demographic groups -- white voters with at least a four-year college degree; white voters without a college degree; African-Americans; Hispanics; Asians; and other minorities.
Now posit that each of those groups voted for Barack Obama or John McCain in exactly the same proportions as it actually did. Then imagine that each group represented the share of the electorate that it did in 1992. If each of these groups voted as it did in 2008 but constituted the same share of the electorate as in 1992, McCain would have won. Comfortably.
...Imagine that the major demographic groups voted as they did in 2008, but cast a share of the vote equal to their expected share of the population in 2020. (For argument's sake, let's divide whites among college and noncollege voters in the same proportions as today.) In that scenario, Obama beats McCain by nearly 14 points -- almost twice as much as in 2008. Demography will indeed be destiny if Republicans can't broaden their reach.
I call this the emerging stagnant majority, because I see it leading to political stagnation, which in turn will reinforce economic stagnation.
I am in the middle of reading Violence and Social Orders, by Nobel Laureate Douglass North, John J. Wallis, and Barry R. Weingast (NWW). The theme of the book is that political and economic development is part of the same process, which they call the social order. The developed world enjoys an open-access order, in which both politics and economics are highly competitive. The rest of the world is in a natural state, in which only the members of the governing coalition are fully free to own property, participate in the political process and--most importantly--form durable organizations.
The United States is currently taking a giant step backward in the direction of a natural state. NWW would say that we are still an open-access order. However, the importance of the rule of law is declining, and the importance of political connections to the elite is increasing. I think we will see this trend emerge much more strongly over the next decade, as it becomes clear that the Republican Party is not going to win another national election. Interest groups will lose hope in competitive elections, and instead they will focus on accomodating the Democrats, which in turn will consolidate the power of the ruling party.
In economics this leads to stagnation, as we shift from an economic system dominated by competition and change from the bottom up to a system of rent-seeking and centralized management. There will be less creative destruction and more redistribution.
In the NWW world, an open-access order avoids stagnation because of political competition. It is in the interest of those out of power to develop attractive alternatives, and it is in the interest of those in power to provide economic growth. However, that assumes a competitive electoral process. The demographic picture, in which traditional Republican voting groups are shrinking as a proportion of the electorate, means that the Democrats have to worry less and less about alienating economic elites, as long as they can maintain an identity politics that appeals to non-whites.
Given this view, libertarians may have the basic economics right when it comes to open borders. Other things equal, more immigration is much better for the immigrants and somewhat better for the native population.
But other things are not equal. Taking into account the effect of immigration on the political equilibrium, Steve Sailer may have it right. We may have seen the last of America as a dynamic economy with a competitive political system. Instead, we may be headed toward a stagnant economy and a one-party political system.