If Mitt Romney can’t start locking up the GOP nomination now, he may never be able to. The former Massachusetts governor’s charmed path toward the presidential nomination was made even smoother Tuesday when New Jersey Gov. Chris Christie opted out of a campaign and recommended that voters choose the candidate with the “best chance” of beating President Barack Obama. No white knight from Trenton, N.J., or anywhere else is riding into the race as the establishment’s savior. Romney’s would-be chief rival for the nomination, Rick Perry, is dropping in the polls amid doubts from conservatives and pragmatists. And the one...