Over the past couple of weeks, it has become clear that Jeb Bush and his campaign have decided to take aim at their most dangerous opponent in the Republican primary. Oddly, their target hasn’t been Donald Trump, who has led the race for over 100 days in the polls, or Ben Carson, who may soon overtake Trump, if he hasn’t already. Bush and his team have instead targeted Marco Rubio, Bush’s one-time protegé and supposed friend. The day after Rubio trounced Bush in response to a personal attack during the debate in Colorado, Team Jeb tried telling donors that Rubio had too much dirt to trust as a nominee — and leaked the briefing to the media:

While the slides released to the press highlight Bush’s Sunshine State endorsements and Rubio’s lack of experience, another page for donor edification gets dirtier.

It’s titled “Marco Is A Risky Bet,” and it bullet-points Rubio’s “misuse of state party credit cards, taxpayer funds and ties to scandal-tarred former Congressman David Rivera.”

When Rubio was a state lawmaker, he used the state party credit card for personal expenses, a decision he later called a mistake. In 2005, he and Rivera jointly purchased a home that later faced foreclosure.

Actually, none of this is a secret, and Rubio has already answered these issues — repeatedly, in some cases. But another line hinted to donors that Mitt Romney and his campaign got scared off of Rubio when they looked deeper:

The most cryptic slight is left for last: “Those who have looked into Marco’s background in the past have been concerned with what they have found.”

A Bush aide says that line refers to concerns Mitt Romney’s team unearthed when they vetted Rubio for vice president in 2012.

That brought an immediate and sharp response from Romneyland:

[I]n an email to POLITICO, Beth Myers, a longtime Romney political adviser who in 2012 oversaw his vice presidential search, pushed back on the assertion.

“As the senior Romney advisor who handled VP vetting and had access to all the vetting documents, I can say that Senator Rubio ‘passed’ our vetting and we found nothing that disqualified him from serving as VP,” wrote Myers, who counts herself a Bush supporter. “The Bush aide referred to in this article is simply wrong.”

ABC’s Rick Klein points out that this defense of Rubio from Myers has a surprising twist:

Fascinating indeed, and perhaps an indication that what remains of Bush’s support may start evaporating as the mudslinging rises. It will be interesting to see whether Team Romney has anything more to say about Bush’s attempts to kneecap Rubio, especially if Bush and his team keep trying to invoke Romney’s name in their attacks.

But that’s just one tactical error among many. Even if one supposes that Rubio is a greater threat to Bush’s path to the nomination than the two candidates who have half of the voters between them, Rubio is the future of the GOP and its most talented communicator as well. No matter who gets the nomination, they will need Rubio’s talents as a surrogate (assuming he’s not on the ticket himself, of course). Bush seems eager to burn the party down not to go after the two leading outsiders, but the third-place candidate who used to be his friend. Not only does that call Bush’s judgment into question, it should have everyone around him looking over their shoulder for a very long while.