Sherrod Brown is Ohio’s hard left, union-hall glad-handing Democratic senator. He’s also considered by many political observers to be Democrats’ best prospective nominee against President Trump in 2020, thanks to profiles like this one from Buzzfeed.

So it’s no surprise that fellow would-be Democratic contenders and their friends and allies might already have their knives out for him. In this case, the dagger-wielders appear to be California Sen. Kamala Harris and endorsers and former staffers of Sen. Bernie Sanders.

Here’s the backstory.

As you might have heard, the GOP tax package contains tax “breaks” for corporate jets.

This sounds downright awful, but in actual fact is kind of a weak hit for reasons the Cleveland Plain Dealer lays out here. The substance is boring, but here’s the real point: The guys who pushed these tax provisions were Sen. Rob Portman and Sen. Sherrod Brown. So, when people pound tables and scream about tax breaks for corporate jet-setters, this is what they’re actually complaining about: Tax treatment that still looks really unfavorable for a lot of people who fly other than on big airlines, and Sherrod Brown possibly having one time in his life done something that doesn’t smack of being a total Democratic Socialist but at the same time is so totally moderate and non-controversial that none other than Sen. Rob Portman got on board with it.

None of this stopped Harris from blasting the tax provision, criticizing it in a statement reported by The Hill and tweeting “Retweet if you would *not* benefit from a private jet tax break.”

Nor has it prevented Jim Dean, Howard Dean’s brother, head of the Howard-founded Democracy for America, and 2016 endorser of Bernie Sanders, from blasting the Brown-Portman provision in an op-ed at the Hill.

And the provision has also been attacked by a former Bernie Sanders staffer via a report he co-authored for the liberal Institute for Policy Studies.

Obviously, any policy that can be shorthanded as “tax breaks for Kim Kardashian and Kanye and their solid gold private Lear Jet” is a tempting target for abuse by Democrats. It’s just convenient that attacking this provision sets up Harris and Sanders, widely viewed as two top contenders for the Democratic nomination in 2020, to attack someone who might prove to be their most formidable foe on grounds that sound decidedly anti-populist (even if the substance is pretty “meh” at best).

Buckle up, folks. 2020 is already well underway. And it’s going to be brutal, bloody, and stupid.