WASHINGTON -- Rep. Tim Walz has become the fourth U.S. House member from Minnesota to line up behind presidential contender Barack Obama, who carried the state handily in Tuesday's Democratic caucuses.

Walz, a freshman congressman from Mankato, cited Obama's overwhelming support in his southern Minnesota district in announcing his endorsement Wednesday. "As a superdelegate to the Democratic National Convention, I will honor their decision and support Senator Obama," Walz said.

Obama defeated New York Sen. Hillary Clinton 67 to 32 percent in Minnesota, one of his more solid Super Tuesday performances. The vote for Obama topped 60 percent in Walz's district.

The Illinois senator had already won the endorsements of Minnesota Democrats Keith Ellison, Betty McCollum and Jim Oberstar. Oberstar came over from the John Edwards camp after the former North Carolina senator dropped out.

Rep. Collin Peterson and Sen. Amy Klobuchar, the other two Minnesota Democrats in Congress, remain neutral in the presidential nomination race.

On the Republican side, Sen. Norm Coleman has endorsed Arizona Sen. John McCain for president. Coleman had supported Rudy Giuliani before the former New York mayor dropped out. Minnesota's three Republican U.S. House members have remained neutral so far.