By PHILIP ELLIOTT
GOLDEN, Colo. (AP) - Republicans in Colorado and Minnesota are holding their presidential caucuses Tuesday, and Mitt Romney is hoping he hasn't ignored Rick Santorum's attacks for too long.
Santorum was rising ahead of the contests after largely bypassing Florida and Nevada. He blanketed Tuesday's states with criticism of Romney and laid the groundwork among conservatives who have greater sway in caucuses.
Rival Newt Gingrich praised Santorum's strategy as shrewd even as he signaled he had no interest in exiting a four-way race that also includes Ron Paul.
Santorum has hammered Romney and Gingrich for weeks. In a sign that his front-running campaign is growing concerned, Romney has been increasing his criticism of Santorum.
Missouri Republicans are having a primary, but it's largely cosmetic because no delegates will be awarded based on the voting.