I expected this topic to be touchy when I previewed it in the Sunday-show thread this morning. I didn’t expect that Bob Corker would find Marsha Blackburn so repugnant that he can’t so much as utter her name when asked about her. He says he’ll vote for “the nominee” for Senate in Tennessee (at one point he refers to her as, gulp, “this person”), but when Dana Bash points out that his endorsement is hardly “ringing” he refuses to take the opportunity to say something more blandly enthusiastic. I’ve never seen an “endorsement” achieve the opposite of its presumptive purpose quite like this one does. Drew McCoy is right: Even Mike Pence’s notoriously lame “endorsement” of Ted Cruz over Trump before the Indiana primary two years ago was better.

Retiring Republican Sen. Bob Corker of Tennessee says he is supporting the Republican nominee to replace him, Rep. Marsha Blackburn, but calls her Democratic opponent Gov. Phil Bredesen his “friend” and says he will not campaign against him #CNNSOTU https://t.co/K7mc898yO1

— CNN (@CNN) April 22, 2018

What’s more amazing is that this morning’s TV appearance looked like it was designed for Corker to make amends after kneecapping Blackburn earlier this week by speaking a bit too fondly of Democrat Phil Bredesen. Here’s WaPo reporting a few days ago:

Asked to assess the state of play, Corker said he guesses that Bredesen is leading Blackburn by roughly six percentage points — a “real six,” he said…

Speaking at a breakfast hosted by the Christian Science Monitor, Corker called Bredesen a longtime friend and described him as a committed public servant. He said Bredesen would have crossover appeal, and noted that a number of top Republican donors in the state were hosting fundraisers for the ex-governor.

“He was a very good mayor, a very good governor, a very good businessperson,” Corker said of Bredesen. “I’m not going to campaign against someone I’ve been a friend with and worked with.”

That sounds like an endorsement. It sounded like one to Mitch McConnell too. He pulled Corker aside afterward to tell him his comments were unhelpful to the cause of retaining a GOP Senate majority, which is certainly true. The party’s facing a tough fight to hold Jeff Flake’s seat in Arizona and may have a surprise battle in Mississippi with Mike Espy for Thad Cochran’s seat. They need all of their other “gimme” states to remain gimmes so that they can pour resources into Arizona and Mississippi (and red states with Democratic incumbents, of course).

Tennessee is supposed to be a gimme but Bredesen’s polling against Blackburn has been surprisingly strong in the early going. And the GOP may have a problem with party unity in the state: Remember, establishment Republicans there are so down on Blackburn’s chances of winning there that some tried to convince Corker to change his mind, un-retire, and run for his seat again. (A Blackburn spokesman later called anyone who believed she couldn’t win a “sexist pig.”) Corker’s problem, though, is that he’d already burned bridges with populists with his stinging criticism of Trump; at least one poll showed Blackburn winning a hypothetical primary with him by a two-to-one margin. So Corker backed off and stuck with retirement, agreeing under pressure from party leadership to “endorse” Blackburn in the name of unity.

Until this week, when he’s done everything he can to signal his support for Phil Bredesen without formally stating it.

What’s stopping Corker from endorsing Bredesen outright? It’d be an act of high treason against the GOP but he’s already headed into retirement. He has nothing to lose except, er, a lot of friendships back home. Chances are, though, that his damned-with-faint-praise “endorsements” of Blackburn are going to lose him those friends anyway whereas a formal endorsement of Bredesen would at least earn him some fawning Strange New Respect from the media as “the good Republican.” All I can figure is that he’s staying nominally on the GOP side of the fence just in case Trump wants to appoint him to something after he retires. But that seems unlikely, as he’s firmly in “frenemy” territory towards POTUS. Maybe he’s playing it safe because he thinks Trump might not run again in 2020 and his successor might make him Secretary of State? Can you imagine how that would play with the base after Corker tried to sabotage Blackburn like this on national television?

Maybe he’s worried that McConnell would strip him of his gavel on the Foreign Relations Committee if he endorsed Bredesen? The whole thing is baffling.