INDIANAPOLIS (Map, News) - Some candidates say the 2008 election is all about change, but voters in Indiana's 7th and 9th congressional districts will see familiar names on the ballots this November.

Five Indiana congressmen won their primary elections Tuesday and four ran unopposed - setting up two key rematches in the general election.

In a special election in March, Democrat Andre Carson defeated Republican state Rep. Jon Elrod with 54 percent of the vote to fill the remainder of his late grandmother's term in Indianapolis' 7th District, an urban district that favors Democrats.

Carson beat seven primary challengers Tuesday, winning about 46 percent of the vote with 99 percent of precincts reporting, according to unofficial results tallied by The Associated Press. Elrod easily won the district's Republican nomination, setting up the November rematch.

Carson urged Democrats to unite as the general election approaches.

"We were divided, but now it's time for us to come together," Carson told cheering supporters in Indianapolis. "We've got another fight ahead of us."

November's toughest congressional matchup will likely be in southeast Indiana's 9th District, where Democratic Rep. Baron Hill faces former Rep. Mike Sodrel, a Republican, for a fourth consecutive time.

It's unusual for two major candidates to run against each other repeatedly, said Robert Dion, a professor of American politics at the University of Evansville.

"Usually somebody takes the hint, but in this case they keep trading the job," he said. "That one is going to be a nailbiter."

Hill was first elected to the House in 1998. He and Sodrel have faced off every two years since 2002 - when Sodrel campaigned as a Washington outsider protecting the interests of voters. Hill won that race with 51 percent of the vote, but Sodrel won by about 1,500 votes in 2004. Two years later, Hill regained the seat.

Losing candidates have some explaining to do if they want to run again, said James McCann, a political science professor at Purdue University. But in Sodrel's case, voters may be more sympathetic toward the 2006 loss because he was one of three incumbent Republicans defeated in Indiana that year as Democrats took control of Congress.

"You can rationalize it: 'It's not about me, it's about the general environment,'" McCann said. "There's some truth there."

The rest of Indiana's incumbents will be favored in November, analysts said.

In central Indiana's 5th District, a GOP stronghold, Republican Dan Burton will likely coast through the general election after defeating a tough primary challenger Tuesday.

Burton - the state's longest-serving congressman - had nearly 52 percent of the vote with 99 percent of precincts reporting, while emergency room physician John McGoff had about 45 percent, according to Associated Press tallies. That's a much closer race than recent primaries, which Burton has won with more than 80 percent of the vote.

"This was a very difficult race," Burton said Tuesday night. "The people of the 5th District want conservative government, want lower taxes, less spending. They want to win the war against terror. They knew where I stood."

Burton came under fire last year amid reports that he missed 19 House votes during a trip to California for a charity golf tournament. McGoff's campaign had played up Burton's travels with a Web site - wheresdanburton.com - that featured photos of the congressman's head on cartoon drawings.

The Democratic primary in the 7th District was also interesting, with Carson defeating several serious contenders: former state Health Commissioner Woody Myers and state Reps. David Orentlicher and Carolene Mays.

Carson had the advantages of being an incumbent and name recognition because of his grandmother, Rep. Julia Carson, who died in December after 11 years in Congress.

Myers poured more than $1.6 million of his own money into his campaign. He finished with about 24 percent of the vote, according to Associated Press tallies.

"I have really no regrets at all, other than the fact that we came in second instead of first," he said.

Republicans Mark Souder in northeast Indiana's 3rd District and Steve Buyer in central Indiana's 4th District also defeated their primary challengers. Indiana's other incumbents - Democratic Reps. Peter Visclosky, Joe Donnelly and Brad Ellsworth and Republican Mike Pence - were unopposed in the primary.

Freshman lawmakers are typically vulnerable because they haven't had much time to establish name recognition, raise money and generate voter support. But analysts expect Donnelly and Ellsworth, who were both elected in 2006, to have little trouble with their general election opponents, Luke Puckett and Greg Goode.

"You're never more vulnerable than when you're a freshman," Dion said. "That ought to spell real danger, but right now it doesn't."

That's because both Donnelly and Ellsworth have much more money than their challengers - cash that could help them hold onto their seats, Dion said.