For years, D.C. Council member Vincent B. Orange has navigated city politics as a self-styled outsider and underdog. The scrappy image goes all the way back to 1990, when as a newcomer he waged a woefully unsuccessful campaign for council chairman against a popular, long-serving fellow Democrat.

Later, Orange’s hard-won victories for seats as a Ward 5 and an at-large member solidified his reputation for going around the Democratic establishment.

But the at-large council member now finds himself trying to explain his relationship with Jeffrey E. Thompson, a former city contractor under federal investigation who is alleged to have funneled $653,000 into a clandestine operation that helped Vincent C. Gray’s successful mayoral campaign in 2010.

Orange is running to hold on to the seat he won in a special election in April 2011, when he accepted $26,000 in money-order donations from Thompson that he now says he considers “suspicious.” The money orders — some bought at the same post office and filled out in similar handwriting — have been linked to Thompson and public relations consultant Jeanne Clarke Harris, who is awaiting sentencing after pleading guilty in the federal probe into Gray’s campaign.

He publicly released copies of the money orders shortly after reporters noted irregularities in donations to his campaign and after FBI and Internal Revenue Service agents raided the homes and offices of Thompson and Harris in March.

Orange said in an interview that neither he nor his campaign staff has received a subpoena for campaign finance records. But throughout his reelection campaign, he has had to address the issue. “There’s not one single penny from Jeff Thompson in this race,” Orange said.

Orange, 55, has raised about $18,000 for the general election, when voters will fill two at-large seats — one held by Orange and the other held by Michael A. Brown (I). One seat is reserved for a non-Democrat.

That Orange, a lawyer and accountant originally from Oakland, is the only Democrat in the race gives him an advantage. The city’s electorate is overwhelmingly Democratic, and turnout among Democrats is expected to be high because of the presidential election. “I’m in great company, running with the president and Eleanor,” he said, referring to Del. Eleanor Holmes Norton (D-D.C.). “That’s the Democratic ticket.”

But Orange and Brown are facing pointed questions from opponents and debate moderators. Brown, son of the late U.S. commerce secretary Ronald H. Brown, has been under intense scrutiny concerning his personal finances. He has failed to pay his rent, mortgage and taxes on time, and he recently said that $113,950 was stolen from his campaign account.

Orange has sought to underscore Brown’s troubles. In June, when they competed for the position of council chairman pro tempore — which Brown won — Orange pointed to his colleague’s tax problems and a past conviction for an election-law misdemeanor.

Brown’s and Orange’s election opponents — Republican Mary Brooks Beatty, Statehood Green Party candidate Ann Wilcox, and independents A.J. Cooper, David Grosso and Leon Swain — have tried tapping into the disenchantment of many voters over federal investigations into city officials and campaigns.

Former council member Harry Thomas Jr. (D-Ward 5) and former council chairman Kwame R. Brown (D), no relation to Michael Brown, resigned before pleading guilty to charges resulting from separate federal investigations. Thomas is serving a three-year sentence for the theft of more than $350,000 intended for youth programs and for filing a false tax return. Brown is awaiting sentencing on charges that he lied on bank-loan applications and violated a city campaign law. Three Gray associates, including Harris, have pleaded guilty as part of the campaign probe.

“Winning is one thing. Being able to serve effectively is one thing. The question is, can you do both?” said council member Marion Barry (D-Ward 8), adding that he believes Orange and Brown can pull off victories Nov. 6.

Orange’s first council campaign, in 1990, was a resounding flop. In the Democratic primary, he took on longtime council member John A. Wilson, the man whose name now adorns city hall, and Wilson came away with 82 percent of the vote. Eight years later, Orange won election to the council from Ward 5.

Orange points to his successes as Ward 5 council member, from 1999 through 2007, pushing for a Home Depot and other retail development and for the reopening of McKinley Tech High School. As an at-large member, he touts legislation to require that third-graders be able to read independently and perform basic arithmetic in order to advance to grade 4. The council approved a measure he sponsored placing a moratorium on strip clubs in Ward 5.

But Orange said the legal and ethical problems swirling around District government and politics have dissuaded him from a massive door-knocking effort. “It hasn’t really been a good climate to go out when we have this cloud of ethics,” he said. “At one point, people didn’t want to hear from politicians.”

Orange lost a Democratic committee vote for his current seat against Sekou Biddle in January 2011. He described that defeat as a coup by an establishment that included Kwame Brown, Thomas and Gray. “All of a sudden people were coming out of closets. I thought: ‘Wow, they got me. I’m out of it,’ ” Orange said.

Orange, however, soon learned that he was polling well against Biddle for the special election to fill the seat in April 2011. “I’m back in with no money and a 20-point lead,” he said. “I start running and asked Jeff for help.”

He said he knows Thompson through Thompson’s philanthropic work with the National Council of Negro Women. When the local Democratic party gave Thompson a lifetime achievement award in 2010, Orange said he presented it.

But Orange said that Thompson is not involved in his campaign and that the campaign is running well without funding from the embattled businessman. “There’s nothing I have not been able to do that I normally do,” he said.