In the wake of Tuesday’s Pennsylvania Democratic Senate primary, a top House GOP legislator is renewing his call for an ethics probe into allegations the White House offered Rep. Joe Sestak an administration post in exchange for foregoing his primary bid against Beltway-endorsed Sen. Arlen Specter.

California Rep. Darrell Issa, the ranking Republican member of the House Oversight and Government Reform committee, said Sestak, who on Tuesday bested Specter by nearly 8 points, must identify the job he was allegedly offered and who in the administration proposed it. Issa has been a one-man firing squad on the point since February, when then-dark horse Sestak claimed in a radio interview an Obama aide had offered him a “high-ranking” federal gig at the onset of his Senate bid.

“Was Joe Sestak embellishing what really happened, or does he have first-hand knowledge of the White House breaking the law,” asked a statement from Issa’s office. “If what he said is the truth, Joe Sestak has a moral imperative to come forward and expose who within the Obama administration tried to bribe him.”

If Sestak and the White House remain mum–and all markers indicate they will–or If the matter is not brought before the Office of Congressional Ethics, the clearinghouse for Capitol Hill ethics probes, Issa warned that he or a fellow member would file an official complaint on July 4.

“I’ve reviewed the capability and appropriateness” of lodging a complaint with the committee, Issa said. “I’m one of many members of Congress considering that it has to be done if he doesn’t come clean.”

If the bribery claim bears any semblance to reality, Issa warned that the White House official who contacted the Sestak may have violated federal law barring election interference and promising employment for political activity.

While President Barack Obama and Vice President Joe Biden congratulated Sestak on his primary victory, the White House’s top press aide demurred on commenting on the controversy, refusing to speculate on the veracity of Sestak’s claims. On Thursday, Press Secretary Robert Gibbs dodged a barrage of Pennsylvania-related questions during his daily briefing, to each he responded: “I don’t have anything to add today.”