Rep. Johnny Isakson, a veteran politician who took Newt Gingrich's former seat in Congress, won the Republican primary Tuesday to succeed maverick Democratic Sen. Zell Miller, whose retirement has given the GOP an excellent opportunity to pick up a Senate seat in right-leaning Georgia.

Isakson will be the immediate front-runner in November against either freshman Rep. Denise L. Majette or businessman Cliff Oxford, who will face each other in a runoff in three weeks after finishing first and second in the Democratic primary.

In North Carolina, former Clinton chief of staff Erskine Bowles faced no opposition and five-term GOP Rep. Richard Burr cruised to the nomination in the race for Democratic vice presidential candidate John Edwards's Senate seat. Two Republicans advanced to a runoff to face Gov. Mike Easley (D), who easily won his primary.

With 98 percent of precincts reporting, Isakson had 333,113 votes, or 53 percent, followed by former Godfather's Pizza chief executive Herman Cain, who had 165,356 votes, or 26 percent. Six-term Rep. Mac Collins was third with 21 percent.

On the Democratic side, Majette had 243,375 votes, or 41 percent, compared with 124,522 votes, or 21 percent, for Oxford, who was recruited for the primary by former president Jimmy Carter.

Majette and Oxford will meet in an Aug. 10 runoff because neither received 50 percent of the vote. In North Carolina, the threshold was 40 percent.

Democrats dominated Georgia until 2002, when Sonny Perdue became the state's first Republican governor since Reconstruction. Perdue also persuaded four Democratic state senators to change parties, giving the GOP control of that chamber.

Miller, 72, a former Democratic governor who was appointed after GOP Sen. Paul Coverdell died in 2000, in many ways symbolizes the state's shift to the right: He often votes with Republicans, strongly backs President Bush and is even scheduled to speak at the Republican National Convention.

The Republican candidates in the Senate race sparred mostly over abortion. Cain and Collins repeatedly criticized Isakson as not being conservative enough, citing his support for allowing abortions in the event of rape and incest.

Cain was only the second black since Reconstruction to run for a top state office in Georgia as a Republican -- evidence, GOP activists said, of their growing base.

The door is open this year for Republicans to make gains in the South. John Breaux of Louisiana, Bob Graham of Florida and Ernest F. Hollings of South Carolina are other Democrats who are leaving the Senate.

In a congressional primary, former representative Cynthia McKinney, a firebrand who lost her House seat two years ago to Majette in a backlash spawned by her incendiary remarks about Bush, was trying to win her seat back in an Atlanta suburb. With 98 percent of the vote counted, she led five other Democrats with 52 percent of the vote; it was too early to tell whether she had enough votes to avoid a runoff.

North Carolina had a full slate of races, including a special election to fill the remainder of the term of former representative Frank W. Ballance Jr. (D), who resigned for what he said were health reasons but also was under investigation over the handling of funds at a foundation he started. Democrat G.K. Butterfield, a former state Supreme Court justice, easily won the election and takes office immediately.

Former Charlotte mayor Richard Vinroot and former state senator Patrick Ballantine were the top two vote-getters in the state's GOP gubernatorial primary -- each capturing about 30 percent of the vote. They are headed for an Aug. 17 runoff.

House co-Speaker Richard Morgan survived a tough GOP primary battle that highlighted a feud that has split the state party. Conservatives said Morgan sold out to broker a power-sharing agreement with Democrats that made him co-speaker.

Rep. Johnny Isakson (R-Ga.), a candidate for the U.S. Senate seat of retiring Zell Miller (D), casts his vote in the primary.