Then, on Wednesday, he posted a quiz on his Web site that accused the GOP front-runner of being ... a "germophobe":
Trump's escalating attacks have gotten personal, too; he has repeatedly called Bush "a low-energy person."
An above-the-fray Bush tried to weather the storm by keeping quiet, choosing to ignore Trump in the hopes he'd eventually go away. But in the meantime, he has dropped into the single digits in some polls. And this week, Bush appears to have spun a 180 on his Trump strategy — the "germophobe" quiz being Exhibit No. 1.
Looks like it felt good to finally go after Trump. Bush's staff couldn't resist trolling the Troll King even further on Twitter:
And apparently Bush has long had a fascination with Trump's reluctance to shake hands:
But if we're analyzing this strategy — which is kind of what we do — we have to note that it has its limits.
Yes, it's true that Trump is a documented germaphobe. He wrote in his 1997 book, "The Art of the Comeback," that shaking hands is "one of the curses of American society. ... I happen to be a clean hands freak. I feel much better after I thoroughly wash my hands, which I do as much as possible."
And Bush kind of has a point that this is not really compatible with being president. Part of a politician's job description is to shake hands — lots of them. An estimated 65,000 a year if you're president of the United States, wrote David Owen in The New Yorker.
But there are some holes in Bush's attack. Developing a fear of germs, in fact, could in fact be considered a hazard of the job. And that includes Jeb's older brother.
In 2013, Owen described how George W. Bush would squirt Purell on his hands after most shakes. He even passed the tip on to President Obama (but not before being called a germaphobe, among other things, for sanitizing his hands after shaking Obama's).
It's a risky move for any politician to go after Trump, whose magic coat of armor seems to only reflect an opponent's attack back onto the opponent. And that goes double when your own former-president brother has faced the same accusations.