OKLAHOMA CITY - Republican presidential candidate Rick Santorum stopped Thursday in Oklahoma City, fresh off a series of primary victories in Minnesota, Missouri and Colorado.

Santorum greeted a crowd of nearly 1,000 supporters Thursday morning at Magnuson Hotel and Convention center near Interstate 40 and Meridian. The U.S. senator from Pennsylvania was originally supposed to make a stop at H&H Gun Range, but organizers received a sudden surge of requests to attend the event, and realized the business would be too small to hold the crowd.

Santorum focused on energy issues during the event. He wholeheartedly endorsed hydrolic fracturing, the controversial method for extracting natural gas using pressurized chemicals to break open gas-bearing rock.

Santorum will stay in Oklahoma and travel to Tulsa Thursday afternoon where he'll hold a rally at Oral Roberts University's Mabee Center.

Santorum's recent wins have caused an upset in the race for the Republican presidential nomination. Many believed Mitt Romney had locked down the nomination, but Santorum's strong showing has suddenly turned this into a two-man race.

The Oklahoma GOP is sponsoring Santorum's visit, but chairman Matt Pinnell said the party's involvement is not an endorsement. The party has extended invitations to all GOP presidential candidates.

Oklahomans will vote in the presidential primary on March 6.