Both John McCain and Barack Obama have touted their ethical standards on the campaign trail, emphasizing that they are politicians who can't be bought.
And they appear to be conscientious of the fine line between constituent services and potential conflict of interest, at least when it comes to the presidential candidates' correspondence with federal agencies, a random sampling of which was reviewed by ABC News over the last year.
In general, most of the correspondence consists of McCain and Obama forwarding letters from constituents concerned about everything from their telephone bills and veterans' benefits to job demotions and patent disputes.
Although constituent services are considered by many congressmen to be an essential part of their duties, congressional rules limit interventions with federal agencies on behalf of constituents. Staffers can facilitate the administrative process, encourage an agency to give a case consideration and sometimes advocate for a favorable outcome. But they "cannot force an agency to expedite a case or act in favor of a constituent."
In the correspondence, many of the constituents' names have been redacted by agencies ranging from the Securities and Exchange Commission to the Pentagon due to federal privacy law so it is impossible to ascertain the results of the inquiries.
McCain, as a senior member of the Senate's Commerce Committee, has sent hundreds of letters to the Federal Communications Commission on behalf of his constituents.
Since the Arizona Senator's involvement in the Keating Five scandal, when he was criticized by the Senate Ethics Committee for "questionable conduct" for meeting with federal regulators to discuss the government's investigation of a savings and loan association owned by longtime contributor Charles Keating, McCain has generally gone out of his way to avoid the appearance of impropriety.
When it comes to constituent concerns, McCain often adds a paragraph to his letters saying that "I ask for no preferential treatment for this petitioner or any single or select group of interests, nor do I advocate a specific outcome for this or any other petitioner."
Mark A. Voigt, a former vice president of Keating's company American Continental Corporation, is a longtime friend of McCain and the current president of the board of directors of the largest private non-profit school in Arizona for students with disabilities.
When he asked for McCain's help to speed up the FCC's decision on a grant to fund the school's computer equipment in July 2005, Voigt wasn't concerned that his association with Keating made him persona non grata with the senator.
"He was always ethical with me. He knows who I am but there was no problem whatsoever," Voigt told ABC News. "There is a difference between going to bat on behalf of a huge corporation and helping some private non-profit agency. He was very helpful – John's a friend of mine. As far as I know, we got the grant taken care of."
Voigt says he never personally spoke with the Senator about the issue and only dealt with his staffers.
And though Voigt is supporting McCain for president, he has not contributed any money to the candidate in over two decades. "Since the Keating days, I try to lay low."
With other old friends, McCain has sometimes been a little more persistent in his correspondence with federal agencies but seems careful not to push it too far.