After several months of reflection, I’m becoming convinced that they are. I don’t claim any private information or special insight. Here, for what they’re worth, are my reasons:

Republican voters are almost exclusively white. And whites, although still a considerable majority, are a shrinking portion of the population. What’s more, Republicans do best among older whites. These voters are, almost by definition, closer to dying out. It’s possible that younger whites will become more Republican as they age: although Obama won a majority of whites under 30 in 2008, he lost that group in 2012. But there’s some evidence that young people of all ethnicities are more socially libertarian and open to big government than their parents.

How can Republicans deal with this forbidding situation? One answer, which has the advantage of inertia, is to do nothing. Actually, that’s not quite accurate. Rather than nothing, Republicans in the House and Senate propose to do exactly what they’ve done in the past. At the moment, that means reviving the Balanced Budget Amendment. As Scott Galupo observes, this is lousy politics as well as bad policy. About 20 percent of Americans name the budget deficit among their main concerns. For the most part, however, they’re already Republicans.

Another strategy is to combine cosmetic outreach to ethnic minorities with concessions on issues that the party establishment considers unimportant, particularly immigration. Marco Rubio appears to be betting his career on this maneuver. That may be wishful thinking. It will take a lot more than quasi-amnesty to win Hispanic votes after years of frankly nasty anti-immigrant rhetoric. And the establishment of a path to citizenship for illegal aliens would both infuriate the base and, over time, dilute its power.

Moreover, Asian Americans, who seem like promising targets for the Republican message, are turned off by Republicans’ assertive Christianity. Parading around converts like Bobby Jindal and Nikki Haley will not be helpful. On the other hand, endorsing gay marriage, say, will drive social conservatives out of the party.

That leaves what might be called the Calhoun option. More popular at the local level than with the national party, at least publicly, this strategy involves legal changes that would limit the influence of the coming majority, which is younger and less white. Some of these measures have been justified by concerns about widespread electoral fraud that are mostly sincere but have no empirical basis. Others are explicitly political. For example, it’s a feature, not a bug, that plans to split states’ electoral votes by congressional district give rural votes greater weight than urban ones (and we know who lives in cities).

As critics of these plans have admitted, there’s nothing new about such efforts: counter-majoritarianism has been a fixture of American politics since the constitutional convention. Even so, they’re unlikely to succeed in the long run. As Tocqueville observed, it’s almost impossible for American institutions to stand against the principle of majority rule.

Contra Karl Rove, however, there are no permanent majorities. The appearance of an unusually talented politician, persistently sluggish economic growth, or an unexpected event such as a major terrorist attack, could lead even more whites to vote Republican in the future. That might be enough to win presidential elections within the next decade or two. And the party will continue to thrive in many states, where residential polarization and gerrymandering give it a built-in advantage.

But it’s tough to see how Republicans can remain a national force so long as their their support is limited to a shrinking cohort. On this point, centrist historians and Pat Buchanan agree. David Brooks, ever the optimist, recently suggested the foundation of a “second G.O.P.” based in the coastal cities, as if two parties with limited, mutually hostile constituencies would fare better than one. They shoot elephants, don’t they?