Sorting out the lobbying entanglements of his campaign advisers is proving to be a messy business for Senator John McCain.

On Monday, just days after it issued new rules to address conflicts of interest, the McCain campaign was furiously sifting through the business records of aides and advisers. The new rules were prompted by disclosures that led to the abrupt departure from the campaign of a number of aides who worked as lobbyists, including some with ties to foreign governments.

Mr. McCain’s political identity has long been defined by his calls for reducing the influence of special interests in Washington. But as he heads toward the general election as the presumptive Republican presidential nominee, he has increasingly confronted criticism that his campaign staff is stocked with people who have made their living as lobbyists or in similar jobs, leaving his credentials as a reformer open to attack.

The process of trying to purge the campaign of conflicts that in appearance or reality might violate Mr. McCain’s stated principles or cause him political trouble has so far focused only more attention on the backgrounds of his aides and advisers.