Three days after Paul Ryan became the presumptive Republican vice presidential candidate, he made a pilgrimage on Tuesday to the Las Vegas gambling palace of Sheldon Adelson, the casino tycoon who is spending more than any other donor to try to send Mr. Ryan and Mitt Romney to the White House. No reporters were allowed, perhaps because the campaign didn’t want them asking uncomfortable questions about the multiple federal investigations into the company behind Mr. Adelson’s wealth.

Those questions, though, aren’t going away, and neither are the ones about the judgment of Mr. Romney and Mr. Ryan in drawing ever closer to a man whose business background should lead them to back away — fast. By not repudiating Mr. Adelson’s vow to spend as much as $100 million on their behalf, the two candidates seem more eager to keep the “super PAC” dollars flowing than to preserve the integrity of their campaign.