Former President George W. Bush is campaigning for brother Jeb this week in South Carolina as pundits debate whether this is a good idea. My take is simple: Not only is this the right call; it’s the only call.

It is axiomatic in politics that if you’re going to be tagged with the negative side of something anyway, you might as well reap the rewards, too. This is why then-Vice President Al Gore (running to succeed Bill Clinton in the wake of the Monica Lewinsky scandal) was politically unwise to distance himself from Bubba. If Gore was going to be punished for Bubba’s sins anyway, he might as well have gotten the full benefit of having a charismatic pol who presided over a period of peace and prosperity out there campaigning hard for him.

Likewise, Jeb Bush is indelibly linked to his famous brother — for good or ill, in sickness and in health, no amount of distancing will matter — so Jeb! might as well reap some of the upside.

This is not to say that it will work, it’s just to say that it’s his only play. Recent polls still have Bush trailing by a large margin in South Carolina, and, it’s not at all clear that George W. Bush’s popularity is transferable to his brother. Former President Bill Clinton, after all, wasn’t able to help his Hillary in South Carolina back in 2008. Nor was he able to push her over the top in New Hampshire this time around.

Still, South Carolina has, for decades, served as the Bush firewall. This goes back to Lee Atwater, the controversial South Carolina operative who ran Poppy Bush’s campaign in 1988. It continued in 2000, when Sen. John McCain’s momentum after a huge New Hampshire victory ran headlong into the Bush buzzsaw in the Palmetto State.

For George W. Bush, there is a real incentive. This a chance to help his brother and defend his legacy. In the wake of Donald Trump’s debate criticism of Dubya, the former president has more than a little skin in this game. Heretofore, President Bush has mostly opted to avoid wading into political waters, but this is an obvious opportunity to do so.

And don’t forget, even though the political milieu has shifted dramatically on the right, there’s still a reason George W. Bush was elected and re-elected. Unlike his more cerebral brother Jeb, “43” has a charisma and a swagger that translated into votes. This was especially true in South Carolina.

Here, I think, Donald Trump may not fully appreciate just how popular George W. Bush was and is in South Carolina — how much he fits culturally in the state — and the psychological connection South Carolinians still have to him. This is a state with a strong military tradition, and buying into the notion that the Iraq War was a waste of time means tacitly admitting that many of their sons and daughters who died did so in vain.

Having said all of that, you might now think this is all about Jeb Bush defending his brother’s legacy-and vanquishing Donald Trump. In fact, Trump seems poised to win there. My guess is this is at least partly about stopping Jeb’s former protege, Marco Rubio, from winning the nomination.

That’s right, I suspect that Jeb Bush has been liberated from worrying about winning and is now running a “joyful” campaign based on spite. Even if he can’t win, Jeb Bush might hope to exact revenge against the young Padawan who turned against him. But even this less ambitious goal seems likely to elude him, as Rubio seems to have surged after the most recent South Carolina debate.

That doesn’t seem to be stopping Jeb Bush from trying to box him out. Paybacks are hell, and politics ain’t beanbag, especially true in South Carolina. Expect things to get uglier before they get better.

Matt Lewis writes for CQ-Roll Call.