Rick Santorum. Photo: wiki commons.

Politico – Rick Santorum’s campaign is eyeing a pair of swiftly approaching Midwestern primary states as its best — and perhaps only — opportunity to deal a mortal blow to Mitt Romney and permanently transform the Republican presidential race into a one-one-one duel to the finish.

Nearly a week after upsetting Romney in the Colorado and Minnesota caucuses and the Missouri primary, both Santorum and his aides say they remain focused on a state-by-state, delegate-by-delegate grind toward the GOP nomination. With Santorum looking increasingly like the last down-the-line conservative standing in the 2012 field, his team sees plentiful opportunities to harvest delegates over the next month in states such as North Dakota, Oklahoma and Kansas — inexpensive political arenas that lean strongly to the right.