MONTGOMERY, Ala. - Alabama's agriculture commissioner on Tuesday overwhelmed a congressman trying to become the first African American to win the Democratic nomination for governor, while four candidates ran a close race on the GOP side.

With 58 percent of the precincts reporting, Agriculture Commissioner Ron Sparks won with 65 percent to U.S. Rep. Artur Davis' 35 percent. Sparks, who is white, had the support of the state's four major black political groups.

In the crowded Republican field, former two-year college chancellor Bradley Byrne, Greenville developer Tim James, and Tuscaloosa physician Robert Bentley were tied at 26 percent each. Former Chief Justice Roy Moore was polling 20 percent.

The top two in the GOP fight will advance to a runoff.

Primaries were also held in Mississippi and New Mexico, and GOP voters in Alabama's Fifth Congressional District were deciding the fate of Rep. Parker Griffith, a Democrat who switched to the Republican Party in December. He was trailing in early returns.

Four-term Alabama Republican Sen. Richard Shelby easily beat his primary challenger, tea party activist N.C. "Clint" Moser.

Two Democrats were vying for their party's nomination, and Shelby, 76, is favored to defeat either one.

Turnout across Alabama was light to moderate.

In Alabama's Democratic primary for governor, the state's traditional civil rights organizations backed Sparks after Davis voted against President Obama's health-care overhaul. But Davis had endorsements from Rep. John Lewis (D., Ga.) and Mobile's first black mayor, Sam Jones.

The health-care overhaul was also an issue in Alabama's other big race. Griffith, a first-term congressman, faced stiff Republican primary opposition from Madison County Commissioner Mo Brooks, who had the backing of local GOP leaders still bitter over losing to Griffith in 2008, when he was still a Democrat.

The north Alabama district traditionally has been Democratic but has leaned Republican in recent years. Four Democrats were competing for their party's nomination for the seat.

In New Mexico, Dona Ana County District Attorney Susana Martinez won the Republican nomination for governor and will face Democrat Diane Denish, the lieutenant governor since 2003, who ran unopposed.

It will be the third woman-against-woman gubernatorial general-election matchup in U.S. history.

The Republicans are hoping to win the governorship after eight years of Democratic control under Bill Richardson, who is term-limited and cannot seek reelection.