If Jeb gets in, it obviously hurts other establishment candidates like Chris Christie and Mitt Romney (it may finally kill the Romney talk). It probably hurts those candidates who could potentially straddle the establishment–Tea Party divide, like Marco Rubio (who will also face the dilemma of running against another candidate from Florida and a former mentor) and Scott Walker. Whom does it help? Ted Cruz. The Texas senator wants a pure establishment–Tea Party fight and a Jeb candidacy does the most to tee that up by potentially squeezing out the candidates who have some appeal to both wings. So Jeb getting in would be the biggest windfall for Cruz since the shutdown fight, without which he wouldn’t be in such a strong position (it gave him an enormous boost among the grassroots and a huge e-mail list). You’ll also see Jeb, if he gets in, probably forming de facto alliances of convenience with other candidates on the activist right. Bush, for instance, would have every reason to root for a strong run by Ben Carson, since Carson’s support presumably comes out of Cruz’s hide and keeps the field to Jeb’s right divided.