After more than seven years of staying out of partisan politics, our 43rd president has returned to the fray. George W. Bush’s willingness to work for his younger brother Jeb’s presidential campaign has put him at the center of a bitter and angry fight with Republican frontrunner Donald Trump. On Monday, the former president spoke at a rally for his brother in South Carolina. Jeb’s campaign is clearly hoping that his brother’s popularity with rank and file Republicans still counts for something, especially in a deeply conservative pro-military state. But while the appearance gave Jeb’s effort the kind of media attention he needs to stay alive, the assumption that W can make a difference in Saturday’s primary in the state may be mistaken.

As I noted after Saturday night’s debate, Trump’s attacks on Bush43 were astonishing not so much because they revealed the depths of the real estate mogul’s animus for the Bush family but because they were taken straight out of the playbook of the far left-wing of the Democratic Party a decade ago. Trump has not paid a political price for any of the outlandish, false, and downright crazy things he has said over the course of the last eight months. Given the bizarre nature of Trump’s performance in the debate, that streak may not hold. But as has been proven again and again, his supporters love him because of his willingness to say outrageous things, not in spite of that trait. The populist surge he has ridden to the top of the polls has been fueled by anger at both party establishments and Trump’s fans revel in his insults and glory in the umbrage they provoke even if what he says is not true or makes no sense.

But let’s assume just for the sake of argument that this time Trump has finally gone too far. Grass roots Republicans do revile their party’s establishment. That’s a generally meaningless term but if means anything it means the Bushes. Yet it seems unlikely that such a conservative electorate would be favorably impressed by a candidate mouthing the sort of conspiratorial attacks on Bush 43 that Trump uttered on Saturday. No one may be in favor of the Iraq War now (and there’s no proof that I’ve seen that shows that Trump was really against it before it became unpopular after the post-invasion insurgency got out of control) but the constituency that would cheer Trump’s blaming Bush for 9/11 and favoring his impeachment is in the other party, not the GOP. Trump may prove the world wrong again, but until it happens pundits are probably on safe ground when they note that recycling Code Pink-style propaganda isn’t the way to win Republican hearts and minds in the South.

But while Trump may not profit from this strange tactic, anyone that is assuming that George W. Bush can put his brother on his back and lift him over the finish line misunderstands the role endorsements play in presidential politics.

A lot of Republicans may still have some affection for W and may be offended by Trump’s attacks. But that is not the same thing as being willing to be influenced by the opinion of someone other than the candidate, let alone pull the lever for dynastic reasons.

Endorsements are not meaningless in presidential politics. They are an interesting and often significant indication of the strength of a campaign and its ability to enlist office holders willing to gamble on backing someone who may or may not win. But on their own they don’t generally mean more votes for the person being endorsed. In the 21st century Americans rarely vote in blocs the way they might have done in earlier eras. Even more to the point, the idea that any personality or politician has the power to transfer their personal popularity to a friend or ally is a myth. Contemporary examples of this sort of thing working are few and far between.

The embrace of his brother is also interesting because it represents a complete abandonment of the strategy the Bush campaign has pursued throughout the campaign. There was a reason why his slogan was “Jeb!” and not Bush! The former Florida governor understood that the last things most voters wanted this year was a recycled dynasty. While most Democrats may be willing, albeit with some clear reluctance that the Bernie Sanders surge has tapped into, to elect another Clinton, Republicans seem to be turned off by the notion of a third President Bush. That’s why Jeb seemed intent on establishing his own identity rather than tapping into the residual loyalty some voters might have for his father and brother. Though George W. Bush may be personally popular among Republicans, most of them understand that invading Iraq wasn’t the only mistake made by his administration. The Bush 43 administration was the last gasp of the kind of big government Republicanism that created the Tea Party insurgency in the first place. The only reason why the Bush cavalry has been called in to try and save him is that the Jeb! approach failed miserably.

We’ll find out on Saturday whether GOP voters will punish Trump for his Michael Moore routine. But there may be no correlation between any potential losses for the frontrunner and gains for Bush. Jeb is locked in a death struggle with Marco Rubio and John Kasich for the lead in the establishment lane and even a small swing in the vote might be enough to earn him third place. But we are fast approaching the point where merely finish ahead of Rubio can be called a victory for Jeb. And with Rubio showing signs of recovering from his New Hampshire debate meltdown and having done a better job defending W than his brother, it’s not clear that any backlash against Trump – if one actually happens — will benefit Jeb.

George W. Bush’s personal reputation as a likable and honorable president who really did labor to keep America safe after 9/11 is not in question, at least not among most Republican voters. But that affection for him or his father is a quality that can’t be transferred from one Bush to another. Though Trump’s attacks made it a bigger deal than it might otherwise have been, Jeb’s playing the W card is still a hail Mary pass being tried by a candidate that doesn’t seem to have any viable path to the nomination.