Since Donald Trump announced his presidential bid, he's drawn plenty of controversy and outrage for his comments on the campaign trail. Here are some of the key moments. (The Washington Post)

Donald Trump is a virulent immigration hard-liner by accident.

Shortly before his presidential announcement speech, Trump's campaign sent out a packet of material for reporters with a press release, information about Trump's finances, and a copy of the "remarks" he would offer from the lobby of Trump Tower included. Marked "as delivered," the draft remarks mention Mexico mostly in passing, saying that Mexico "is not our friend. They are beating us at the border and hurting us badly at economic development." The introduction Trump planned to offer said only, "ISIS, China, Mexico are all beating us. Everybody is beating us. "

That's not the speech Trump delivered. Instead, he offered the sort of stream-of-consciousness rant that has become the hallmark of his still-young candidacy. While he was still warming up, he talked about ISIS and China in more detail, then offered his now-infamous description of Mexico. The country is "sending people that have lots of problems, and they’re bringing those problems with [them]," he said. "They’re bringing drugs. They’re bringing crime. They’re rapists." Coming up for air, he added, "And some, I assume, are good people."

In part thanks to the fact that he kept rambling for another half hour, the comments about Mexicans didn't cause many ripples right off the bat. Nor did Trump immediately seize upon immigration as a campaign issue. The closest he came was a fight with Hillary Clinton after she declared that his rhetoric on Mexicans was the sort of thing that could trigger someone to commit an act like the shooting in Charleston. Trump went after Clinton; he didn't talk about the urgency of illegal immigration. Beyond that exchange, the comments didn't come up at all. On Twitter -- which serves as a sort of transcription of Trump's brain -- he mostly complained about President Obama, retweeted praise, and got in a fight with Neil Young.

It wasn't until Univision spoke out about Trump's comments that said comments moved to the center of the conversation. And very quickly, Trump realized he had a winner.

To thousands of people, it didn't matter that Trump's initial scattershot defense of his comments was wrong, that illegal immigrants aren't more likely to commit crime than those here legally. Nor did it matter, it seems, that Trump eventually shifted his defense to imply that he'd meant that the Mexican government was sending criminals across the border. For an apparently substantial (or at least very vocal) part of the electorate, simply calling out illegal immigrants as bad in broad strokes was enough reason to rise to Trump's defense. Trump, whose reaction to praise is Pavlovian, instantly realized it.

Interestingly, the Republican establishment that's so eager to have Trump vanish bears some of the blame. After Mitt Romney's 2012 loss, leaders in the party recognized that they needed to figure out a way to either embrace or neutralize the Hispanic vote before 2016. There was a big strategy document and repeated attempts to figure out a "comprehensive immigration reform" package. A package passed the Senate only to be ignored in the House, where conservative opposition was much stronger. Last summer's immigration crisis -- and the media firestorm that greeted it -- compounded the problem, but the defeat of House Majority Leader Eric Cantor in Virginia's congressional primary stopped it cold. Cantor's defeat was trumpeted in the conservative media as being a reaction to his advocacy of immigration reform.

Whether or not that's why Cantor lost -- a strong argument can be made that it wasn't -- his defeat made clear the split within the party. There is an establishment that wants to figure out how to soften the party's position on immigration in hopes that it can entice Hispanic voters. And then there is a very loud and very frustrated part of the base that wants no such thing. Donald Trump's random attack on "illegal immigration" had the same effect as George Clooney and the Soggy Bottom Boys singing "Man of Constant Sorrow" in "O Brother, Where Art Thou?" The crowd went wild, he had no idea why, but he jumped on top of the wave.

Trump is at least self-aware enough to realize it. In an admirably frank interview, our Robert Costa asked Trump why he decided to seize on immigration. Trump's response? "They gave it to me. It wasn’t a big part of my announcement speech — a small paragraph."

Immigration is never really what Trump wanted to talk about. That may be one reason that his "solutions" to illegal immigration are so nonsensical: Build a giant wall (with Mexico somehow being enticed to foot the bill), and charging Mexico $100,000 per illegal immigrant (though Trump doesn't know how many illegal immigrants there are).

Or they may be nonsensical because Trump has never really thought seriously about how to fix this or any other political problem. Perhaps -- perhaps! -- he's just in it for the applause. Once that applause tapers off, it's hard to imagine Trump pursuing his candidacy with any real gusto -- unless he accidentally pushes another hot button and hears distant clapping. In which case, that's the direction he's likely to head.

Reince Priebus and the GOP have ten fingers and ten toes crossed that he doesn't.