Rick Santorum’s trio of victories in Tuesday’s contests in Colorado, Minnesota and Missouri virtually assures that the Republican presidential race will, on some level, be a delegate race.

And if that delegate race drags on for a while, it could very well pit different regions of the country against one another.

First, here’s why a delegate race is looking more likely:

Ron Paul and Newt Gingrich were already pledging to stay in the race for the long haul, and both have shown an ability to amass delegates. Santorum’s staying power was the big question mark in all of this, but he’s now a good bet to be a factor come Super Tuesday on March 6.

Republican presidential candidate and former Pennsylvania senator Rick Santorum speaks during a primary night watch party Tuesday in Missouri. (AP Photo/Jeff Roberson)

Also, the proportional nature of the delegate process in most of the early states means a few candidates can win delegates in each state and it will be much harder to build a big delegate lead. In fact, AP projections based on Tuesday’s results have Santorum claiming second place in the delegate race, and he could dramatically shrink Romney’s lead by Super Tuesday if he fares well in the contests before then.

And lastly, if there’s anything that this race has shown us so far, it’s that the momentum created by particular victories can turn on a dime. So even if Romney sweeps the two primaries held Feb. 28 in Arizona and Michigan, for example, we really can’t say with any certainty that he’ll translate that into a sweep on Super Tuesday.

“I think the results leave us with a scattered field,” said Tennessee Republican National Committeeman John Ryder. “We are past the ‘battle of annihilation.’ Nobody has been knocked out. All four remaining candidates have the ability to raise money and continue their fight.”

So what would a prolonged delegate race look like?

Well, if the early contests are any indication, the race could be a pretty regional one, with Gingrich winning the South, Santorum winning the Midwest and Romney winning elsewhere. After all, Santorum has now won three Midwestern states, including two by huge margins, and Gingrich seems to be reverting to a kind of Southern strategy that relies heavily on those states south of the Mason-Dixon Line.

In the end, a win is a majority of the 2,286 delegates at stake, and if those delegates are being split four ways, it becomes much harder for one candidate to reach a majority — 1,144 delegates.

Here’s our best guess at how that might pan out, in a series of phases:

(And for all the latest on the delegate race, make sure to bookmark the Post’s great Republican Primary Tracker, which contains full details on how many delegates each state has, how they allocate them, etc.)

Feb. 28 – Arizona and Michigan primaries (59 delegates)

Arizona’s primary is winner-take-all for its 29 delegates, while Michigan will award its 30 delegates on a more proportional basis.

Romney has good inroads in both these states, with a significant Mormon population in Arizona (see: Nevada caucuses) and with his father having been governor of Michigan. But he has also been hammered over his position against the auto bailout, which could hurt in the Wolverine State.

The real battle here seems to be Michigan, which could pit Romney’s inherent strengths against Santorum’s blue-collar Midwestern appeal. But the real delegate prize is Arizona, so the smart money will be spent there if the campaigns are preparing for a delegate race.

March 6 – Super Tuesday (437 delegates)

Ten states will hold GOP contests this day, including primaries in Georgia, Massachusetts, Ohio, Oklahoma, Tennessee, Vermont and Virginia, and caucuses in Alaska, Idaho and North Dakota. Essentially all of these states have some kind of proportional system of allocating delegates.

Gingrich figures to do well in Southern states like Georgia and Tennessee, but he failed to qualify for the ballot in a third, Virginia. Romney will obviously do well in his home state of Massachusetts and probably Vermont too. Santorum may connect with blue collar workers in Ohio. And Paul has some caucus states where he can steal some delegates; he took at least 17 percent of the vote in 2008 an all three of these caucus states.

The key battles here are most likely to be in Ohio, where most of the 66 delegates are available, three at a time, to the winner of each congressional district. That could be a big swing if a candidate sweeps the state, and it’s why we’re already seeing Gingrich and Romney focus here.

But also look at Oklahoma, which is kind of a hybrid of the Midwest (Santorum’s strength) and the South (Gingrich’s strength).

In other words, there are constituencies here for everyone to win, and it could be close if all the candidates are still seen as viable.

The rest of March (430 delegates)

Eleven more contests will be held in March, with the big ones being primaries in Alabama, Illinois, Louisiana and Mississippi, along with key caucuses in Kansas and Missouri.

This may be Romney’s toughest stretch, as most of these states are either Southern or Midwestern. But he will have an advantage in the biggest state, Illinois (69 delegates), both because it’s a more moderate state (despite being Midwestern) and due to a complicated delegate-selection process that favors an organized campaign.

April (484 delegates)

This is where a delegate race would start getting decided, because it is when every state can start allotting delegates on a winner-take-all basis.

Yet the biggest April states – Texas and New York (250 delegates combined) – are still proportional, which means the race could continue even after April if those states are split up sufficiently.

Gingrich is counting on Texas, but it’s too simple to just label it a Southern state. New York would obviously seem to be Romney territory, but again it’s not clear-cut. Santorum, meanwhile, should do well in his home state of Pennsylvania and Midwestern Wisconsin.

May (276 delegates)

Seven contests this month are highlighted by the Indiana and North Carolina primaries on May 8, but this month includes no pure winner-take-all contests.

The regional advantages at this stage are harder to mete out, but there are some Southern states (Arkansas, Kentucky and North Carolina) and some Midwestern states (Indiana and Nebraska) for Gingrich and Santorum to play in.

June (339 delegates)

This is really when winner-take-all starts to take hold. California is the big one (172 delegates), but there are also 90 delegates at stake in winner-take-all contests in New Jersey and Utah. Both New Jersey and Utah are pretty clearly Romney Country, so it’s a nice backstop for him if he winds up in a real delegate scrap.

If it got to this point, it would almost certainly become all about California on June 5.