When fourth or fifth is better than third

(CNN) - If third place finisher Tim Pawlenty is out, why are Rick Santorum and Herman Cain, the fourth and fifth place finishers at the GOP presidential straw poll Saturday in Ames, Iowa still in the race for the White House?

One answer: Size matters.

Pawlenty, the former Minnesota governor, came into the crucial straw poll with a large, experienced and expensive campaign staff, while Santorum, the former senator from Pennsylvania, and Cain, the former CEO of Godfather's Pizza and radio talk show host, are running for the Republican presidential nomination on shoestring budgets.

In an interview with this reporter Saturday night, minutes after the results of the straw poll were announced, Santorum described his campaign as "'The Little Engine that Could' campaign. No matter what happens, we're just going to keep plugging away."

And he compared himself to Pawlenty, who finished just over 600 votes ahead of Santorum: "We were in range of three. I mean I felt like here's a guy who spent a million bucks in this and we spent a fraction of that and here we are within a few hundred votes of him and I feel very, very good about that. I feel we're positioned exactly were we want to be."

Cain was equally tough on Pawlenty's effort, telling CNN Chief Political Correspondent Candy Crowley Sunday on CNN's "State of the Union" that Pawlenty "made a big investment, and he doubled down as we call it, and it didn't pay off."

"We didn't put a million dollars into the straw poll," added Cain. "We spent zero on the TV and we spent zero on the radio, and so this campaign is encouraged and our momentum continues to grow."

GOP strategist and CNN contributor Alex Castellanos says expectations are one reason Pawlenty is gone and Santorum and Cain are still in the hunt for the White House.

"Pawlenty's problem is that he lost, not because he wasn't known but because he was. He had money, time, organization and exposure. If he couldn't make the case with all of that, how could he going forward?"

Castellanos, who was a top media adviser to the 2004 Bush-Cheney re-election campaign and to Romney's 2008 bid for the GOP presidential nomination but is not taking sides in this battle for the Republican nomination, adds that Pawlenty "traveled farther and faster than Cain or Santorum, but he reached the end of his road."

Follow Paul Steinhauser on Twitter: @PSteinhauserCNN.