While his campaign has cited its volume of small donations as a rationale for his decision to opt out of public financing for the general election, Senator Barack Obama has worked to build a network of big-dollar supporters from the time he began contemplating a run for the United States Senate.

Over the years, Mr. McCain has nurtured a reputation for bucking the Republican establishment and criticizing the influence of special interests in politics. But an examination of his leadership of the Republican institute reveals an organization in many ways at odds with his image as a political outsider.

So far, Senator McCain, the presumptive Republican presidential nominee, has received more than $181,600 from lobbyists and trade groups, while his Democratic rival, Senator Barack Obama, has received just over $6,000. Senator Hillary Rodham Clinton, who ended her bid for the presidency in June, got more than $87,000.