The short answer: Not until he’s sure that Rex Tillerson isn’t getting Borked. If T-Rex goes extinct, Trump will need a Plan B at State. Giuliani and Bolton probably can’t get out of committee due to Rand Paul’s opposition, and Petraeus is a nonstarter due to his history with classified information. There’s only one man sufficiently respected by Republicans and sufficiently inoffensive to Democrats to be confirmed easily.

But let’s face it, Tillerson’s not getting Borked. Rubio will do plenty of throat-clearing about the threat from Putin’s Russia but he’s not going to take the heat of voting against Tillerson in committee when hawks like Dick Cheney and Condi Rice have vouched for him. He’ll fold. Maybe you’ll lose McCain and Graham in the floor vote, but if every other Republican votes yes as a goodwill gesture to the new president, Tillerson can get confirmed with Mike Pence as the tiebreaker even if every Democrat votes no. Which is unlikely: A few Dems from conservative states, like Joe Manchin, will roll over.

So back to the main question. Once Tillerson is confirmed and Romney’s officially out of the running for a cabinet job, when will he feel comfortable criticizing Trump again? I’m leaning strongly towards “never.”

How does Romney now speak out when Trump next disgraces himself & the country on something Romney cares about?

— David Frum (@davidfrum) December 13, 2016

One obvious reason for Romney to keep his mouth shut from now on is that no one in the cabinet, including Tillerson, will be there for eight years. Some won’t even be there for four. Trump, remember, went through three campaign managers in the span of three months this summer. There’ll be turnover, and Romney could be looked at for various positions — State, Treasury, an ambassadorship, even the VA, where a “turnaround specialist” is desperately needed. According to literally every account published of the Secretary of State selection saga (here’s the latest one from Politico), Trump really did seriously consider Romney for the job. It wasn’t a goof or a revenge plot. It was legit. And if he was open to the idea this time, he’ll be open to it when there’s another vacancy. If Romney wants to be eligible for that, he’ll have to maintain a respectful silence about Trump’s missteps. He’s already done it, kinda sorta: Apart from a CNN interview early this past summer and an occasional Facebook bulletin (e.g., after the “Access Hollywood” tape dropped), Romney didn’t have much to say about Trump during the general election campaign. He can hold his tongue when he thinks criticizing Trump might do more harm than good.

Even if Romney doesn’t care about a job, Trump could probably keep him on his side simply by seeking out his advice now and then. Keep him inside the tent pissing out, as LBJ was known to say, instead of outside the tent pissing in. Trump seems to have taken the same approach with Obama so far, calling him periodically during the transition to consult. Obama has been conspicuously restrained in criticizing him in turn. Trump could follow that practice with Romney, giving him a call every few months to chat about some policy or other. If Romney knows he has a pipeline to Trump to express his concerns, he’ll be less likely to express them publicly. (Same goes for every other Republican, which is why Trump would be smart to make “friends” with other critics in the same fashion.) Although, for Trump, maybe it pays to have Romney outside the tent pissing in under certain circumstances. Having Mr. Establishment attacking him periodically would help Trump shore up his populist cred among the Republican base if/when he does something to alienate them. It’s not like Romney is some widely beloved figure among grassroots righties. He attacked Trump viciously during the primaries and then again a few times during the general election, and look how that turned out for Trump. That’s another reason to believe that Trump’s newfound fondness for Romney is probably genuine — Romney’s more valuable to him as a foil than as an ally.

Then again, perhaps Romney still has a tiny bit of grassroots cred left after all:

“This is man who came out big-time against Trump. Oh, the things he said about Trump. Well, that’s great, that’s wonderful,” [Harry] Reid said. “Either he wasn’t telling the truth, or he’s a person with no character. After having said that, to go and do homage to this guy he said awful things about, I don’t think that shows much character.”

“Mitt Romney is somebody I had respect for,” Reid said, in a somewhat dubious assertion. “I have none anymore.”…

“I was indeed very critical of Mr. Trump during his campaign. But now he has been elected president and accordingly, if I could have helped shape foreign policy to protect the country I love, I would have been more than willing to do so,” Romney said through a spokesperson. “As for Mr. Reid, I lost respect for him when he repeatedly lied about my taxes and later admitted to it cheerily. Good riddance, Mr. Reid. The Senate will be better served without you in it.”

The only way Romney turns on Trump, I think, is if Trump crosses some very basic line as president. Don’t think “detente with Russia,” think “trying to strip flag-burners of their citizenship.” If, in other words, Trump turns into the worst case scenario of himself that Romney warned about during the primaries, I think Romney’s sense of what duty requires will shift from “serving the country in the cabinet if the president asks” to “opposing the president vocally.”

Exit question: How about Romney as ambassador to Russia? If Trump wants to reassure hawks that he and Tillerson aren’t going to do Putin’s bidding, putting a guy who’s famous for calling Russia our number one geopolitical foe on the Moscow diplomacy team would do it.