(CNN) - It's election day in Alabama, again.
Voters head to the polls to cast ballots in runoff elections six weeks after the state's June 1 primaries.
The biggest contest is the battle for the Republican gubernatorial nomination. Bradley Byrne, a former state senator and former chancellor of the state's community colleges, faces off against state Rep. Robert Bently. Byrne came in first in the primary, with Bently edging out businessman Tim James by less the 300 votes for second place.
The winner faces off in November against Alabama Agriculture Commissioner Ron Sparks, the Democratic nominee. The race is to succeed Republican Gov. Bob Riley, who is term limited. Riley announced Friday that he would vote for Byrne.
Also up for grabs Tuesday is the GOP nomination for the state's second congressional district. On the ballot are Martha Roby, who served two terms on the Montgomery city council, and businessman Rick Barber, who's won the support of many Tea Party activists. Roby came in first in the primary, but Barber has captured national attention for a provocative web ad that rails against what's described as an oppressive federal government and urges voters to "gather your armies."
The winner will face freshman Democratic Rep. Bobby Bright, who narrowly won the district in 2008.
In the seventh congressional District, the Democratic nomination is up for grabs, with Attorney Terri Sewell facing off against Jefferson County Commissioner Shelia Smoot. The race is to succeed Rep. Artur Davis, who lost badly to Sparks in the Democratic primary for governor.
Alabama is a rare state that allows people who voted in one party's contests in the primary to cast ballots in the other party's contests in the runoff.
–Follow Paul Steinhauser on Twitter: @psteinhausercnn