HOWEVER, if he'd been outmaneuvered and gored by a force half his size in another masterpiece of manuver warfare, almost identical to the performance Lee had turned in against Hooker the year before...report to Washingon for further orders, General. I don't believe it would've been equivalent to Grant being defeated in an attack upon Lee's works, no matter how bloodily repulsed, because there's always tomorrow, and another flank march. But at North Anna...too many dead and no good way forward would've compelled Grant to go all the way back. And that would've finished him AND Lincoln. Lincoln had backed him all the way from Ft. Donelson and the first rumors of drunken incompetence, through Shiloh when the Army of the Tennessee had been shamefully surprised and almost destroyed (being saved only by the timely intervention of the Army of the Ohio), the long Vicksburg campaign that seemed to take forever and was only helped by a half-witted performance from his counterpart; and the pressure to get rid of Grant, despised as he was by everybody that didn't actually understand the man's qualities (VERY few were aware of the pure gold that Grant represented), was enormous, so if Grant had been defeated comprehensively, Lincoln's judgement (and remember: nobody really liked Lincoln, either) would've been seen by the electorate to be faulty. Lincoln would've paid for his faith in Grant at the polls in November.
We got SO lucky; if Lee and Hill had been on top of their respective games...lights out. Even Grant saw after it was over what Lee tried to do, and it must've given him night-sweats to think about it. He never again put himself and the Army of the Potomac in a position where Lee could crush a wing at a time, like Lee was wont to do if presented with the opportunity.