House Oversight and Government Reform Committee Ranking Member Darrell Issa wants to open an ethics investigation on Pennsylvania's Democratic Senate nominee, Joe Sestak.
Issa (R-Calif.) has long pressed Sestak (D-Pa.) and the White House over allegations that Sestak was offered an administration post in exchange for quitting the Senate primary.
Sestak was running behind Sen. Arlen Specter (D-Pa.) at the time the offer was allegedly made. He didn't get out of the race, and this week defeated Specter to win the nomination.
According to Issa's office, he or another lawmaker will file a formal request to the House ethics panel by July 4 if an outside group does not do so beforehand.
If the White House did make Sestak the offer, it could violate federal law. Republicans have sought to make the allegations a big issue.
The White House has remained mum on the accusations, and press secretary Robert Gibbs declined to answer questions about the matter at his weekly press briefing on Thursday. In March, he said that he spoke to other officials about the offer and described the conversations between the White House and Sestak as not problematic.