Everywhere you look, in the year of Donald J. Trump, observers are talking about a national party realignment or a Republican death spiral. Our two-party system has not undergone a major realignment since the South became solidly Republican. There has not been a major-party demise since the Whigs collapsed on the eve of the Civil War.

Mr. Trump (or Ted Cruz) could very well lead the party to a decisive and divisive defeat. If it was catastrophic enough, it could lead to changes in party strategy. Yet predictions of a Republican crackup should be greeted with skepticism. While rumors of the death of the Republican Party have been common in recent presidential elections, they have proved again and again to be vastly exaggerated.

The gap between expectations and political realities reflects two mistakes: The first is to overestimate the centrality of presidential contests to our system of checks and balances.

The second is to misunderstand the recent Republican electoral successes — which rest less on effective governance than on attacking government, and especially the occupant of the Oval Office.

It is not simply that the G.O.P. enjoys these structural advantages (strength in rural areas, edge in low turnout off-year elections). More and more, it feeds on the failure of its presidential standard-bearers. Party leaders sincerely lament these repeated losses (and may come to lament them more with the Supreme Court’s balance now on the line). They are not trying to win by losing. But they are doing just that, and this tells us a lot about how the contemporary Republican Party works.

Republicans excel at generating and then exploiting hostility to government, and thrive on being in opposition, especially to presidents. Almost without fail, recent presidential losses were followed by a “backlash” election — in 1994, 2010 and 2014 — in which the G.O.P. swept to victories in Congress and statehouses.

Given the current dysfunction of the Republican Party, many both inside and outside Republican ranks are probably hoping that a big defeat will force the party to change. But waiting, as the current president once put it, for the “fever” to break may be fruitless.

Try this setup instead: It’s 2017. After Mr. Trump’s landslide defeat, President Clinton has a Democratic Senate and House of Representatives. The Republican National Committee has just released its latest post-mortem — it probably looks a lot like the post-2012 soul-searching exercise, the Growth and Opportunity Project, which encouraged moderation in tone and inclusiveness in policy.

But that blueprint is ignored. Instead, the party quickly regroups in opposition to the incoming administration. Most Republican voters hate Mrs. Clinton even more than they hated Mr. Obama. The conservative apparatus for sowing discontent with a new administration is in place, flush with cash and battle-tested.

For Republicans in and outside government, it will be a time not for facing up to hard truths but for doubling down on hardball tactics.

American voters choose presidents, not kings (or queens). American political institutions are, and were designed to be, a complex system of interlocking parts. The drama of presidential campaigns should not blind us to these longstanding and deeply rooted dynamics or to their perverse effect: They allow the Republican Party to thrive even as its presidential candidates do not.

More worrisome, they reinforce a dangerous spiral. The most effective Republican response to its own unpopularity in presidential elections is to take steps to make the American political system more unpopular still.