BIRMINGHAM, Ala. — Republican Newt Gingrich says he'll campaign for president until the party's nominating convention in August, but his candidacy largely rests on the results of primaries Tuesday in Alabama and Mississippi.

Asked by reporters how he felt about his chances, Gingrich said: "Pretty good."

The former House speaker is banking on a Southern strategy that so far has yielded two victories: in South Carolina and Georgia, which he represented in Congress for 20 years. So winning Tuesday's contests is vital to keeping his campaign going.

Gingrich was spending Tuesday in Birmingham, where he addressed a local Chamber of Commerce about his plans to modernize the federal government if elected president.

"The reason I stay in this race is it's about more than right versus left. It's about being smart, it's about understanding the modern world," he said.

Gingrich planned to be in Illinois on Wednesday to campaign for the March 20 primary there.

In Alabama and Mississippi, polling shows a tight three-way race among Gingrich, Mitt Romney and Rick Santorum.

In an address Monday to a Republican presidential forum in Birmingham, Gingrich implored voters to support him.

"I've stayed in this race for two reasons," he said. "I do not believe the two other candidates can beat President Obama. We have to win in a principled way with a big enough agenda and enough momentum to change Washington decisively."