Sen. John C. Stennis (D-Miss.) easily won renomination for a seventh term in Mississippi yesterday, while West Virginians chose a conservative congressman to oppose Senate Minority Leader Robert C. Byrd (D-W.Va.) in November.

New Mexico Democrats picked state Attorney General Jeff Bingaman to challenge Republican Sen. Harrison H. Schmitt, and both parties chose candidates for governor. In South Dakota, Democrats nominated state Sen. Mike O'Connor for governor.

West Virginia

Byrd, minority leader in the Senate since early last year, had no primary challenge. But a spirited contest is expected this fall, against Rep. Cleve Benedict, who won the Republican primary.

With 1,377 of 2,294 precincts reporting, Benedict had 42,248 votes, James Washburn 5,205 and Fred Weiland, a retired Army officer, had 4,164.

In the 1st Congressional District, where Democratic Rep. Robert H. Mollohan is retiring, his son, Alan, led state Sen. Dan Tonkovich in a field of six candidates. With 70 percent counted, Tonkovich had 16,506 votes and Mollohan, an attorney, 16,858.

Mississippi

Stennis overwhelmed state Sen. Charles Pittman and radio station owner Colon Johnston for the Democratic nomination.

With 99 percent of the vote counted, Stennis had 146,642 votes, or 74.8 percent, while Pittman had 33,658 votes, or 17.6 percent, and Johnston had 14,420 votes, or 7.6 percent.

Haley Barbour, 34, a Yazoo City attorney who was state campaign manager for Gerald R. Ford in 1976 and Ronald Reagan in 1980, easily won the Republican contest. He defeated Bobby Richardson, 45, a member of the Mississippi Highway Commission.

With 97 percent of the vote counted, Barbour had 30,461 votes, or 74.3 percent, and Richardson had 10,531 votes, or 25.7 percent.

New Mexico

In the race for the Democratic nomination to oppose Schmitt, Bingaman defeated former Gov. Jerry Apodaca. With 792 of 1,209 precincts reporting, Bingaman had 62,867 votes, Apodaca had 42,940 and Virginia Keehan 7,217. Schmitt defeated a write-in candidate.

Under state law, Democratic Gov. Bruce King cannot run again, and primaries in both parties were staged to pick his successor.

Former attorney general Toney Anaya won the Democratic gubernatorial primary, defeating former state senator Aubrey Dunn and Fabian Chavez Jr. With 792 of 1,209 precincts reporting, Anaya had 65,299 votes, Dunn 43,819 and Chavez 7,053.

In the Republican contest between two former state senators, real estate dealer John Irick had 23,683 votes and builder Bill Sego 18,034.

Rep. Manuel Lujan Jr., seeking his eighth term, won 87 percent of the votes to defeat E.G. Martin of Albuquerque in the 1st District GOP primary. Jan Hartke, son of former senator Vance Hartke, was unopposed in the Democratic primary.

In the Democratic race in a new House district created by reapportionment, consultant Bill Richardson held a slight lead over Lt. Gov. Roberto Mondragon, District Judge George Perez and attorney Tom Udall, son of former Interior Secretary Stewart Udall and nephew of Rep. Morris K. Udall (D-Ariz.)

Marjorie Bell Chambers, a Los Alamos educator, led economist Dwayne Jordan in the GOP contest.

State Sen. Caleb Chandler of Clovis led Sen. Ben Altamirano of Silver City in the Democratic primary in the 2nd District. GOP incumbent Joe Skeen was unopposed.

South Dakota

State Sen. Mike O'Connor defeated former state representative Elvern Varilek in the Democratic primary for governor. With 92 percent of the vote tallied, O'Connor had 22,809 votes and Varilek 15,484. Republican Gov. William Janklow was unopposed.