Mitt Romney is still in control of the nomination, and you can still ignore talk of the still-implausible contested convention. But yesterday’s victories by Rick Santorum have made another, different GOP nightmare scenario that isn’t getting any attention far more likely.

Call it the Winning Ugliest outcome.

What could happen is this: Romney could end up winning the delegate count, securing the nomination. But at the same time, Santorum could rack up enough wins — and end up leading in national polls — leaving a huge chunk of Republicans thinking he’s the rightful winner. This could possibly create a GOP nomination split that’s hard to heal heading into the general election.

Imagine weeks and weeks in which Republicans revisit last night’s results: big headline victories for Santorum, but solid delegate gains by Romney. Romney’s strong states in the rest of the calendar tend to be winner-take-all; Santorum’s tend to allocate their delegates more proportionately. So Romney could win fewer remaining states but reap far more delegates from them.

Santorum is still having significant organizational difficulties; he’ll lose some delegates in Illinois because he couldn’t file a full slate, and he didn’t get on the Washington, D.C., ballot. We don’t know much about what’s happening with delegate selection in the caucus states, either, as they move from the precinct caucuses to later rounds that actually choose delegates. Santorum is counting on his conservative credentials to help him in those, but Romney’s organizational strength and support could trump ideological considerations among delegates, enabling him to do well among them.

Santorum may also soon open up a national polling lead, particularly with big headlines now calling Santorum a winner.

Of course, it’s possible that Romney will wind up winning the headlines in the next several weeks, just as he won Ohio and Michigan. The most likely outcome is still an eventual stampede for Romney in April or May. But this other, Winning Ugliest, scenario still exists; right now, it’s more likely than ever; and if it happens, it would make the Obama campaign very happy.