Take it from me, senator: Never go full RINO.

No, no, kidding. The bad news? If you were hoping to see a few Cruz missiles lobbed at Republicans like Mitch McConnell in the primaries next year, you’re out of luck. The good news? If you were hoping to vote for him for president in 2016, this suggests that, yeah, he’s thinking about running.

At a closed-door lunch meeting of Senate Republicans Wednesday, the freshman conservative told his colleagues that he would not intervene in their 2014 primary fights or fundraise for the controversial outside group. Cruz added that the [Senate Conservatives Fund’s] decision to try to defeat sitting GOP senators in their primaries was its alone, according to several people familiar with the session.

According to one source familiar with the meeting in the Senate’s Mansfield Room, Cruz noted that Republican Sens. Mike Lee of Utah and Rand Paul of Kentucky wouldn’t fundraise for the group and promised that his image would be removed from its materials. Senate Minority Leader Mitch McConnell (R-Ky.) told Cruz that Paul took such an action six months ago, but he thanked the Texas conservative for doing so. Other GOP senators also thanked Cruz, sources say…

One source said Cruz made clear to his colleagues at the Wednesday meeting that he would not associate himself with the group any longer. But a Cruz spokeswoman said the senator would still be involved with the group’s effort in “promoting conservative causes.”

Senate Republicans allegedly first got in Cruz’s face about the SCF back on October 2, the day after the shutdown began. They asked him to renounce the group but he refused. The new promise not to campaign against anyone while maintaining his relationship with the SCF is a sort of compromise. Then again, if Cruz is still going to work with the group on “causes,” does it much matter that he won’t be formally endorsing any primary challengers? E.g., if a new deal is forged on immigration reform next summer and Cruz turns opposition to it into another grassroots cause celebre like the “defund ObamaCare” episode, any GOP incumbent who backs the deal will be seen as having failed the new litmus test and implicitly will have earned Cruz’s disfavor. Formal endorsements mean much, much less to voters than a candidate’s record on passing litmus tests, I think, and Cruz has almost unrivaled power at the moment in setting ideological litmus tests for his colleagues. He doesn’t need to explicitly say “Support Mitch McConnell’s challenger” when he’s going around accusing the Senate GOP — led by Mitch McConnell, of course — of having bombed its own troops in the House by making a deal to end the shutdown. The SCF’s press shop can “clarify” whom he meant by that when it runs ads against McConnell, even if Cruz doesn’t appear in them himself.

But if Cruz’s nonaggression pact with the rest of the caucus is really just a big loophole to keep attacking them, then my theory that this is a sign that he’s running is no good. A presidential candidate needs friends in Congress, the more powerful, the better; that explains 80 percent of Rand Paul’s surprisingly warm relations with McConnell, I assume. Endorsements may matter less than litmus tests but they do matter a little, and a big mass of them for one candidate versus another might matter a lot. The risk to Cruz in 2016 is that he ends up with no allies in the Senate (except maybe Mike Lee) and and no legislative achievements to point to when people question his experience because no one in the Senate outside of tea partiers much wants to partner with him. (I think Matt Lewis is right that that’s also driving Lee’s moderate-sounding rhetoric this week. He wants to get stuff passed, and you need allies in the middle to do that.) If that isolation persists and Cruz ends up locked in a RINO/conservative death match with Chris Christie, there may be a tidal wave of Christie endorsements from Republicans in Congress and that will affect some voters in the big mushy “somewhat conservative” middle. Then again, even making nice with his colleagues might not change that; centrists in Congress will break for Christie anyway, and there may be nothing Cruz can do now to convince “defund” skeptics that he’s a guy they can trust with the most important job in government. He’s gone to great effort lately to brand himself as the Senate’s most outspoken populist. Maybe the only way to leverage that is to exploit the “conservative cause” loophole to the hilt and start setting as many litmus tests as he can. If the Beltway hates him for it, so much the better. That only proves that he’s an authentic outsider.