Dear Republicans: I see you couldn't help yourself. You've nominated Donald Trump for President of the United States. Really. His obvious psychological problems didn't stop you, or his obvious stupidity. They may have even been selling points. You are going to rue this day for a long time. But what's really remarkable is that you, who have been one of the two major parties for a century and a half, have nominated a third-party candidate for president. Congratulations, I suppose.

That is what Trump is: a classic third-party candidate, someone who is ultimately in the race as a protest against the establishment and who is there to advance issues that aren't on the major parties' agenda. Those candidates tend not to be electable themselves, and not to have the qualifications they would need to actually do the job, because they aren't in the race to get elected. They are there to change the conversation. And that's certainly true of Trump. He couldn't do the job, and no reasonable person thinks he could. He doesn't even know what the President's job is.

("Separation of powers" is apparently a foreign concept to The Donald, because -- let's be honest here -- The Donald is a terrible American.)

You have nominated third-party-protest candidate Trump because you, the Republican Party, are now a protest-oriented third party. That's been increasingly true for a while, but now it's official. You're a third party in a second party's position, which has been bad for the whole country. The system is designed for two parties, and it breaks down if one of them acts like a third party instead. The country pays a heavy price for that behavior, but your party is going to pay a heavier one.

You haven't had a governing agenda for years. I mean, you haven't even pretended. You've focused everything on opposing the Democrats, tearing down rather than building up, and you've focused most of all on things that you know you can never pass into law. That disregard for what can actually get done is the hallmark of a third party. What were all those dozens of votes to repeal Obamacare for, except to establish that you were a fringe party with no interest in anything but empty symbolism? When you vote for the same thing sixty-two times without doing it, you are telling the entire world that you don't matter and that you don't want to matter.

What about your endless parliamentary shenanigans and hostage-taking, repeatedly threatening to default on the national debt if you aren't given whatever fairly small-bore demand you're obsessed with on that particular week? That is the textbook tactic of a minority party in a multiparty system, like the fourth or fifth party extracting concessions by threatening to leave a governing coalition. You're basically like some goofy faction in the Italian parliament, or one of those tiny Israeli parties composed of idiot rabbis. They also demand what they want by threatening to bring down the whole government, and they also do it for relatively petty goals. That's what being a third or fourth party is about: being free from the burden of doing anything.

And then you pushed out your own Speaker of the House for the high crime of not actually shutting down the government or defaulting on the national debt. The crime of making deals. And there's nothing a third party hates more than making deals. They're usually free from that burden because they can't get to the bargaining table in the first place. That isn't your problem yet, but it will be. It might just take a while.

Nominating Trump makes it clear what you have become. At this point, you are nothing but an ethnic party, a vehicle for aggrieved white people's tribal animosities. Trump excels as a standard bearer for that party. He is totally miserable at building the wider coalition you would need if you ever want to win another national election. But your voters have spoken, and that's not what they want. They want to be the aggrieved losers. The good news is that everyone who lobbies for that job eventually gets it. Palookaville has plenty of space for you, and you can stay forever if you like.

Right now, the Trump Republican party is a rump Republican party, based on ethnic resentment. It's built on a coalition of the old Southern Dixiecrats and the uglier elements of the Reagan Democrats in the North and Midwest. Your party is now analogous to France's National Front, Italy's Northern League, the UK Independence Party, or the various right-wing nationalist parties in former Communist nations. Of course, there are many of you, and many long-term Republican constituencies, who don't fit in such a party. But right now, that race-based nationalist coalition is in charge, and the rest of you are being told to go along with the new party line or get out.

The Trump Republican party is just looking for white tribal advantage. Its core appeal is identity politics, expressed as demonization of outsiders: blacks, gays, Latinos, Muslims, transgender folks who need to pee. That would be enough to win a nationwide election in 1904. But it's not enough any more, not when you throw in some woman-bashing and a candidate who's unfit to govern. The basic appeal of the Trump candidacy is that any white man is more qualified than a black man or a woman, intelligence, experience, and fitness for office notwithstanding.

But this attempt to return to a white monopoly on political power comes just as demographic trends demand that a shrinking white majority share power with other ethnic groups. Indeed, it is largely a response to that truth, which Trump's supporters find upsetting. This white identity politics is enough to win you some elections, a lot of elections, on the state and local level, but not enough to win the White House. And that vote will only get smaller over time.

Welcome to your third-party world, Republicans. Some of your party members will be leaving, of course, becoming independents or Democrats or members of some third party that knows it's a third party. A lot of your Wall Street and Chamber of Commerce wings will likely be heading for the exits. Maybe the next major party will coalesce in time around some of those ex-Republicans. Maybe the Democrats will eventually bifurcate. These realignments don't happen often in our history. Or maybe you'll turn it around and build your way back to major-party status. But you're going to spend a long time in the wilderness, because you're doing things that will take decades to live down. You can't run as the White Power Nationalist Front for one election and then just act like that never happened. Believe me, what you're doing right now is very, very memorable.

You can't nominate an openly unqualified candidate and expect people to keep taking your party seriously. If you don't take yourself seriously, why should we? And your establishment figures can't endorse Trump and keep their credibility. Those two things don't go together. If you are willing to stand next to Trump and smile, like one of his beauty pageant contestants, you've established that there's nothing you won't do. Why should we ever think you are motivated by substance?

You don't want to govern, Republicans. You've made that very clear. And you've also made it clear that you're no longer fit for the job. If that's not the message you meant to send, I'm sorry. That is the message that you have sent, and everyone else has heard it.