DENVER | Sen. Barack Obama is trying to portray himself and his running mate, Sen. Joseph R. Biden Jr., as the "outsider" ticket of the year, but Mr. Biden's 35-year career in the Senate may make that a difficult sell. One need look no further than Mr. Biden's relationship with his lobbyist son and his law firm to see why.
Mr. Biden's campaign has hired lawyers from his son's firm to do its legal work. His son's firm lobbied for the University of Delaware and, in turn, Mr. Biden championed federal funding for lucrative projects, known as earmarks, in congressional spending bills.
In addition, Mr. Biden's son, Hunter, once worked for MBNA, the giant credit-card company, whose employees are the elder Biden's largest source of campaign contributions and whose side Mr. Biden took in a controversial bankruptcy-law fight.
All of which makes Mr. Biden a veteran of the types of insider fights that "outsiders" are supposed to eschew. "He's no stranger to how the system works," said David Williams, vice president of policy for the Citizens Against Government Waste.
Republicans are seizing on the ties between Mr. Biden and his son's lobbying firm, calling Mr. Biden "a model Washington insider with numerous connections to lobbyists and special interests," said Danny Diaz, spokesman for the Republican National Committee.
But Mr. Obama's campaign, which refuses donations from federal lobbyists, downplayed the criticism and said that the senator's son has never lobbied his father on behalf of any clients or employers.
"All the Republican spin under the sun can't change the fact that Joe Biden has a 35-year record fighting for people when powerful interests have stood in the way of the public interest, whether it's drug companies, oil companies or insurance companies," Obama spokesman David Wade said.
According to Federal Election Commission records, employees of Oldaker, Biden & Belair LLP have done legal work for Mr. Biden's political campaigns. This year alone, the lobbying firm earned $140,000 in legal fees from Mr. Biden's presidential bid.
Last year, the former treasurer for Unite Our States, Mr. Biden's political fundraising committee, was Phu Huynh, a lawyer who works at Oldaker, Biden & Belair. David McNitt, former custodian of records for the Biden campaign fund, also works at the lobbying firm as a legislative assistant. The firm did not return phone calls Monday for comment.
The University of Delaware over the years has paid more than $1 million in lobbying fees to Oldaker, Biden & Belair and the National Group, an affiliate.
This year, Mr. Biden and and fellow Delaware Democrat Sen. Thomas R. Carper secured two earmarks worth more than $400,000 for the university, according to Citizens Against Government Waste, a nonpartisan group that tracks earmarks and opposes congressional spending that it considers excessive.
The university has received more than $5 million in earmarks since 2004, the group said.
University spokesman Neil Thomas said R. Hunter Biden was part of the Oldaker, Biden & Belair law firm that created the National Group, "but he did not directly work with" the university.
Mr. Thomas said the university decided to drop its lobbying contracts this spring and will no longer employ a Washington lobbying firm. The university praised the elder Biden's efforts on its behalf.
"As a Delaware senator, Senator Biden has always been responsive to representing the University of Delaware's interests on federal matters," Mr. Thomas said. "He and his staff have been supportive of a number of university funding priorities, and that support predates the university's hiring of the National Group."
Some employees of the lobbying firm who have contributed to Mr. Biden's campaigns won't be allowed to do so now because they're federal lobbyists, and Mr. Obama has banned lobbyist from contributing to his campaign.
William Oldaker, who gave $4,600 to Mr. Biden's presidential campaign, has lobbied for dozens of clients over the past decade, including powerful corporations such as Delta Air Lines, Xerox Corp. and tobacco giant Phillip Morris, Senate records show.
Some of Mr. Biden's biggest political support has come from the financial services industry, including more than $200,000 from employees at MBNA Corp. in Delaware. The New York Times reported that Mr. Biden's son also has worked as a consultant for MBNA from 2001 to 2005.
Mr. Biden also supported a bankruptcy bill favored largely by Republicans and MBNA, while Mr. Obama has criticized the legislation on the campaign trail.
Mr. Wade, the campaign spokesman, said Mr. Biden's son never lobbied his father on MBNA, either.
"I want to be crystal clear. Hunter Biden has never lobbied Senator Biden's office or committees, period," Mr. Wade said. "He's never worked on a client issue where other members of the firm have lobbied the office. Hunter has never lobbied for MBNA. Senator Biden has been as strong a supporter of ethics reform as the Senate has known, and his office follows all ethics laws right down to the letter."
Mr. Wade also said Mr. Biden "took plenty of hard knocks" from MBNA, the state's largest employer, by demanding changes in the bankruptcy legislation.
"Senator Biden improved the bill for low-income workers, women and children," Mr. Wade said. "There were times when he believed amendments on both sides would have blown up a bipartisan compromise backed by three-quarters of the Senate. At those moments, Senator Biden had to make the tough calls, and he voted to pass a bill."
The 2005 law that Mr. Biden supported overhauled the bankruptcy system and made it harder to file for Chapter 7 bankruptcy - which consumer groups widely opposed, but which benefited banks and credit-card companies.
On Monday, Mr. Obama railed against banking lobbyists for blocking mortgage industry reform that, he said, could have averted the current housing industry crisis.
"I've been saying we need to crack down on the mortgage lending and financial institutions for years, but the problem was that the banks and the financial institutions ... all spend hundreds of millions of dollars on lobbying and campaign contributions," Mr. Obama said.
• S.A. Miller contributed to this report.