Tuesday’s three-state caucus sweep by Rick Santorum illustrated the degree to which many conservative voters remain skeptical of Romney’s commitment to the GOP base’s principles, especially given what some of them see as his history of shifting priorities. And he hasn’t been able to sell them on his main argument – that he’s the most likely in the primary field to beat Democratic President Barack Obama.

“The more confidence the strong conservatives have in the alternative candidates, the more Romney’s lack of strength in those categories starts to show itself,” said Iowa Rep. Steve King, a conservative who has been publically neutral in the nomination race.

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