GOP Tries to Tip Balance in Key Primary Races for House : Politics: Eight states hold contests. Voting shapes up ballot challenges for the fall election.

Republicans picked New Jersey’s Assembly speaker to challenge Sen. Frank R. Lautenberg (D-N.J.) in one of the key races on Tuesday’s primary ballots critical to GOP hopes of capturing the Senate in November.

There was voting in eight states, and lineups for more than 80 House races were being set. Only a few incumbents faced significant primary challenges.

Lautenberg easily defeated two primary opponents Tuesday, but he is considered among the most vulnerable Democratic incumbents this fall. State Assembly Speaker Chuck Haytaian, who also won easily, has portrayed Lautenberg as a big-spending liberal.

In Mississippi, Republican Sen. Trent Lott cruised to victory over two little-known challengers and is heavily favored to win a second term in November.

Republicans need to gain seven seats to control the Senate for the first time since 1986, a daunting but not impossible task given recent Democratic setbacks and the high number of contests that were competitive.

In addition to Lautenberg, another Democratic incumbent on the GOP’s target list is Jeff Bingaman of New Mexico, who had no opposition in Tuesday’s primary. Bingaman already has been under attack by former Pentagon official Colin McMillan, who was favored to win the Republican nomination to face him in November.

Montana also had a Senate primary. GOP Sen. Conrad Burns was unopposed, but he won six years ago with 52% of the vote and is considered vulnerable. The Democratic contest was between former Sen. John Melcher and attorney Jack Mudd.

In governor’s races, Republicans Terry E. Branstad of Iowa and Walter Dean Miller of South Dakota needed to fight for their party’s nomination Tuesday.

Branstad’s first hurdle to an unprecedented fourth term was moderate Republican Rep. Fred Grandy, the former actor on the “Love Boat” television series.

Miller moved up from lieutenant governor last year when George S. Mickelson was killed in a plane crash. Miller’s bid for a full term faced primary opposition from former Gov. Bill Janklow.

On the Democratic side, Alabama Gov. Jim Folsom and New Mexico Gov. Bruce King were challenged from within their party. Early returns had Folsom leading Paul Hubbert, a teacher’s union leader. Republicans had crowded fields in both states.

For all of the talk of the public’s anti-incumbent mood this year, there has been little revolt so far at the polls. Heading into Tuesday’s voting, only two House incumbents had fallen in primaries.

The primary also marked the end of an era in Mississippi politics: Democratic Rep. Jamie L. Whitten is retiring after a record 53 years in the House.

The Whitten seat was one of six on Tuesday’s ballot in which there was no incumbent running. It also was one of a dozen House seats in Southern and border states now in Democratic hands that Republicans have a chance of capturing in November. The GOP has won special House elections already this year in Oklahoma and Kentucky.