He managed to burnish a reformer's reputation while swimming in the muddy waters of special-interest- infested state politics.

He worked on a nice-guy image while practicing the hardball and brawling tactics of Chicago-style politics.

Now, promoting himself as a fresh face on the national political stage, proclaiming his distance from lobbyists and the Washington culture of special interests, Sen. Barack Obama (D-Ill.) has to contend with his own history.

From Chicago to Springfield, his past is filled with decidedly old-school political tactics -- a history of befriending powerful local elders, assisting benefactors and special interests, and neutralizing rivals.

Obama may be packaged as something new among presidential contenders, but in this town where politics is played like a blood sport he fit right in.

"He knows how the game is played," said Jay Stewart, executive director of Better Government Assn., a nonpartisan group that honored Obama for helping overhaul state ethics law. Stewart called Illinois politics "deeply troubled, if not corrupt" at its core.

"It is very difficult to come out of a system that is flawed and walk out unscathed. Sen. Obama has done better than most. But it's not as if he is a babe in the woods," Stewart said.

In fact, Obama's first venture into politics suggested he came to the game ready to throw elbows. That was in 1995. He had been invited to succeed Alice Palmer when she left the state Senate to run for Congress.

He reached out to local power brokers and financial backers -- among them entrepreneur Antoin Rezko and politically connected Al Johnson, a retired auto dealer who was the late Mayor Harold Washington's bridge to the business community.

Palmer backed Obama too. But friendly succession hit a bump when Palmer's congressional bid failed. She asked Obama to step aside and let her run for her old seat in the state Senate.

Obama did more than refuse. The onetime voting rights activist in Chicago's poor districts challenged the signatures qualifying Palmer for the ballot. Palmer was disqualified, and Obama, then 35, took office running unopposed.

"Some can say it was cold, but that is how the game is played," said Illinois state Sen. Donne E. Trotter, a Democrat whose district bordered Obama's.

That first race cemented ties with Johnson and Rezko that have spanned Obama's political career. Both made significant donations. And Rezko became one of Obama's most important patrons. He and his associates are responsible for $160,000 in campaign aid over the past 12 years.

Rezko has helped numerous politicians from both parties. In 2003, he gave President Bush $4,000 and co-hosted a fundraiser in downtown Chicago said to have generated $3 million for the president's reelection.

But Rezko also represents another rule of old-style politics: Beware of your friends. Last fall, Rezko was indicted here on federal public corruption charges, forcing politicians, including Obama, to distance themselves.

Armed with ambition

Obama arrived in Springfield with another familiar tool from the kit of Chicago politics -- ambition.

Cynthia K. Miller, who ran his district office, recalls an incident shortly after Obama's election. She had taken a longer-than-normal lunch break and returned to find an impatient state senator waiting for her.

He didn't raise his voice, she said, but he turned stern as he explained the importance of time management and the need to focus on goals. Then he shared his own goal: "I plan to be president."