It’s not unusual for a 65-year-old to announce his retirement, but a lot of people were caught by surprise when Sen. Bob Corker of Tennessee did so on Tuesday. In a statement, the senator, who has found himself increasingly at odds with President Trump, said he he hadn’t planned to serve more than two terms in office. But is there more at work in the departure of this influential senator than simple adherence to a self-imposed term limit? What does it portend for the Republican Party establishment, Trump and the future of the party? There are a few ways to think about it.

1. The Establishment Collapse narrative

Political Twitter’s initial reaction to the news of Corker’s retirement was to collectively gape at the terrible day that Senate Majority Leader Mitch McConnell was having. Corker is a key McConnell ally in the Senate, and there’s a chance that he could be succeeded in 2018 by much less of a team player. The latest attempt by the Republicans to repeal Obamacare was officially declared dead, and McConnell’s horse in Alabama’s U.S. Senate primary, Sen. Luther Strange, seemed likely to lose to the Steve Bannon-backed Republican, Roy Moore (who won after all).

The idea that Republican leadership had yet again failed to come through on Obamacare was damaging enough (getting rid of the law was one of their central promises to the base during the Obama years). But Moore’s win in deep-red Alabama against Strange, who had been endorsed by the president (albeit quite tepidly in the end), seemed to demonstrate that the establishment wing of the party might well be ineffective under Trump. Corker’s decision to throw in the towel on a day of such resounding loss for McConnell and friends seemed all the more poignant.

2. A head on a stake for Trump

Corker’s decision to step down doesn’t come out of nowhere, of course. I wrote just this week about a few unlikely scenarios that could shake up the 2018 Senate map, and one was that Corker would lose to a more Trumpian primary challenger. Corker, who was once considered a top contender to be secretary of state, raised Trump’s ire by criticizing the president after Trump failed to condemn white supremacists in Charlottesville, saying that “the president has not yet been able to demonstrate the stability nor some of the competence that he needs to demonstrate in order to be successful.” Trump criticized Corker shortly after — in a tweet, of course — intimating that Corker ought to be booted from office.

Bannon, Trump’s nationalist former senior adviser, was rumored to be looking for Corker challengers, and it’s possible that Corker was eyeing Arizona Sen. Jeff Flake’s rough polling numbers in his contested primary and biting his nails.

The Trumpian wing of the Republican Party seems out to pick off establishment figures in the 2018 election, and Corker’s decision to bow out could be read as something of a victory for the president and the Bannon types in the party — the head on the stake displayed for all to see, a warning that if you come at the king, you best not miss.

Maybe …

3. Corker’s ‘Take-’em-Down-With-Me’ mission

Although Corker might well have stepped aside to avoid a brutal primary challenge, he seems unlikely to go gentle into that good night. The statement announcing his decision contained a rather interesting little passage:

I also believe the most important public service I have to offer our country could well occur over the next 15 months, and I want to be able to do that as thoughtfully and independently as I did the first 10 years and nine months of my Senate career.

What does Corker think might happen over the next 15 months? (A request for comment from Corker’s office had not been returned by the time of publication.) For one thing, as head of the Senate Foreign Relations Committee at a time when there is much talk of Russian interference in the 2016 election, he could launch an investigation, as other congressional committees have done. Or he could simply step up his criticism of both the president and the Trump campaign’s possibly cozy relations with Russian influencers. In the early months of the Trump administration, Corker was vocal in his criticism of Russia. In December, he promised his committee would thoroughly review Russian hacking during the 2016 election, but in February, he stopped short of endorsing an independent commission to look into it. He has pushed for stronger sanctions against Russia, so it’s clear that he cares about the issue. But in July, a Tennessee paper called him out, saying that he’d been too quiet on the issue of Trump’s seeming affinity for Putin’s Russia. Corker told the paper: “I’m a guy you talk to on policy issues. Find somebody else to talk to about politics.”

It might be that with 15 months to go, Corker is willing to go out in kamikaze fashion: His political career might be dead, but he’s more than willing to set fire to some things on the way out.