That be where were we diverge, I think regardless of who wins the Republican nomination, they will also win the general as the seemingly capped Democrat anxiety(think Carvelle and Cadell) swells underneath the surface, the difference will be to get enough Senate and House seats and carry out a conservative agenda, I see Newt as being more able as the message he has conveyed during this campaign echos well everywhere...
I think Newt would bring more down-ballot GOP gains than Romney would. If the GOP selects Romney as its standards bearer, many will stay home. If the GOP selects Romney as its standards-bearer (and it seems inclined to do so), some will work to defeat the GOP. I know I'll work to defeat a party of liars and liar-enablers.
You could be very well right though, that the GOP will take the presidency regardless. There are hoards of people who will support the GOP as the lesser of two evils.