(CNN) - Primary voters are set to head to the polls this weekend, this time in Louisiana and West Virginia.
In Louisiana, GOP Sen. David Vitter is expected to easily overcome a primary challenge Saturday in his first appearance on the ballot since a 2007 prostitution scandal.
In West Virginia, voters are choosing the Democratic and Republican nominees for a November special election to replace the late Sen. Robert Byrd, a Democrat.
Vitter is being opposed in the Republican primary by former state Supreme Court Justice Chet Traylor and Nick Accardo. Tulane University political science professor Brian Box said after Traylor's last-minute entry into the race, "it seemed like it could be an interesting primary."
When he announced his challenge, Traylor said that "we wouldn't be in this position if we had a senator who could get results." He ran a radio ad targeting Vitter over "family values," and cited a Vitter aide's arrest on domestic abuse charges.
But with little money and questions raised about Traylor's past, Box said that, in the end, Traylor's campaign "never became anything."
With polls showing him holding a large lead, Vitter has spent most of his time in the primary focusing on the general election, not his Republican opposition.
Vitter's advertising "is almost entirely against [likely Democratic nominee Charlie] Melancon," Box said. "There was nothing against Republicans."
Melancon, the congressman from Louisiana's 3rd District outside New Orleans, is the favorite in the Democratic Senate primary against Cary Deaton and Neeson Chauvin.
The nonpartisan Rothenberg Political Report rates the general election as "favored Republican."
Several U.S. House primaries are also on the Louisiana ballot, including the race for candidates seeking Melancon's seat. Republicans believe they have a chance to pick up the seat, the only one in the state currently in Democratic hands. Box said three major Republican candidates have been competing, "trying to out-tea party each other."
Meanwhile, four Democrats are competing to challenge vulnerable GOP Rep. Joseph Cao in his New Orleans district. The race has been targeted by national Democrats as a seat considered vulnerable in November. The seat was held by Democrats until Cao was elected to replace former Rep. William Jefferson, who is serving a 13-year prison term after his conviction on corruption charges.
Cao initially voted with House Democrats on health care reform, but voted against the final version of the bill.
"Cao is in a lot of trouble," Box said. Democrats have focused "so much on defending turf, [but] this is a chance for a pickup."
In West Virginia, both parties will select nominees for the general election race for the seat of Byrd, who was serving his ninth term in the Senate when he died in June at age 92.
Gov. Joe Manchin is expected to win the Democratic nomination over two opponents, including 95-year-old Ken Hechler. Hechler was a four-term secretary of state and represented West Virginia in the U.S. House from 1959 to 1977.
On the GOP side, 10 candidates are competing for the nomination, including businessman John Raese, who was defeated by Byrd in 2006.