A highly unwelcome prospect has crept into Democrats’ heads in recent days: Sen. John Fetterman could complicate their already difficult path to the majority by switching parties.

The nightmare scenario for Democrats goes like this: They could flip the necessary four seats in the November midterms — by picking off difficult red states like Alaska and Ohio — only for Republicans to successfully win over the Pennsylvania Democrat and rob them of the majority. Politico’s Jonathan Martin has reported there’s just such a recruitment effort afoot on the right.

Fetterman’s Washington Post op-ed on Thursday saying he has “no plans to leave” the party should make Democrats feel better — but not completely.

Because their Fetterman headaches are going nowhere.

The first-term senator noted that, despite bucking his party on some high-profile issues recently, he still votes overwhelmingly with Democrats and sides with them on issues of abortion, labor, marijuana and labor rights.

He criticized his party for what he cast as knee-jerk opposition to whatever President Donald Trump does and suggested it has changed, rather than him.

But he concluded: “I’d be a terrible Republican who still votes overwhelmingly with Democrats.”

The first thing to note is that while some have cast this as Fetterman rejecting a party switch, he didn’t fully rule it out.

Yes, it’s significant that he even felt pressured enough to write this op-ed downplaying the prospect, and Democrats should be heartened that he did.

But “no plans” is not the same as “no chance,” and politicians often use the former phrasing to keep their options open. If things were to change, Fetterman — who’s not facing reelection until 2028 — could say he truthfully wasn’t planning on switching parties, but that his plans changed because of XYZ.

And plans can change, as we learned in a very similar situation in the same state 17 years ago.

It was March 2009, and prominent Democrats were publicly lobbying Republican Sen. Arlen Specter to join their side. They hoped he would give them a 60th vote and massively important filibuster-proof majority.

When I sat down with Specter that month, he threw cold water on the idea. He said it was possible he would run for reelection in 2010 as an independent (he was facing a very difficult Republican primary). But he made a principled argument for why the Senate needed a robust minority party and said wouldn’t run as a Democrat.

Less than a month and a half later, Specter became a Democrat, making it abundantly clear his party switch was about political survival.

These two situations are not the same. For starters, Specter, a longtime moderate Republican, had a decent chance of winning a primary as a Democrat. (He wound up losing 54%-46%.) Fetterman probably harbors few illusions about winning a GOP primary.

But it might be even more unlikely Fetterman could win a Democratic primary. A recent Quinnipiac University poll showed 73% of registered Republicans in the state said they approved of his handling of the job, compared to just 22% of Democrats.

And even if the party switch is off the table, that doesn’t mean the drama is.

While the Senate has a long history of moderates who quietly vote against their side when it mostly doesn’t matter, Fetterman seems to relish torturing his party by breaking on some very high-profile issues — and then going on Fox News to talk about it.

That includes the wars with Iran and in Gaza, government shutdowns, Cabinet nominees and other issues.

And what Fetterman calls his “independent voice” is also a highly combustible situation for Democrats because of who he is and where he comes from.

While Democrats for years bemoaned West Virginia Sen. Joe Manchin’s tendency to cross over and vote with Republicans, he came from one of the reddest states in the country. Democrats should have been glad they got any votes from a West Virginia senator.

Fetterman, by contrast, comes from a swing state where a standard-issue, anti-Trump Democrat would probably be competitive. That will continue making Democrats mad.

And then there’s the future majority math.

Even if Democrats win a Senate majority this year, it’s likely to be a very narrow one — probably 51-49, unless the 2026 election is an absolute Democratic rout in which they win a state like Iowa or Texas.

In that scenario, Fetterman could be a very important swing senator. Imagine there’s a Supreme Court vacancy, and Democrats want to keep it open until a new president is elected, like Republicans did in 2016. At that point, they’d need to keep Fetterman onside.

Indeed, the safest play for Democrats right now is to play nice with Fetterman, even if that’s not easy or cathartic.

If nothing else, the last few days have reminded them that he could hold some serious cards.