He can win a Senate seat, the Democratic presidential nomination and maybe even the White House. But for presidential candidate Sen. Barack Obama (Ill.), there will always be the one that got away.

Eight years ago, Rep. Bobby Rush (D-Ill.) crushed Obama by a 2-1 ratio in a primary that marks the first and only time the Land of Lincoln Senator has lost an election.

Reflecting on the eve of Obama’s historic Thursday night speech at Denver’s Invesco Field at Mile High — to be delivered exactly 45 years after the Rev. Martin Luther King Jr. delivered his “I Have a Dream” speech on the steps of the Lincoln Memorial — Rush said that he’s watched proudly during the past decade as Obama has transformed from a local one-trick pony to a mature politician.

“Barack was a young man, wet behind the ears, and he didn’t understand retail politics,” the former Black Panther said during an interview at the Denver Marriott yesterday. “He was very articulate and was a tough campaigner, abreast on some of the issues, but he had no record.”

“I had a history of working on behalf of my constituents in my community,” he continued. “The Lord decided that I was doing a good job.”

At times sounding like an aging prizefighter still confident in his ability to go 12 rounds, Rush said he now regularly jokes with Obama about his 2000 primary victory, frequently reminding his colleague that “I cleaned his clock.”

The 62-year-old ordained Baptist minister, who is recovering from cancer treatment, also portrayed a deeper kinship, recalling recent discussions with his colleague about the lessons Obama walked away with after the contentious 2000 primary, which pitted a green state Senator against a powerful South Side Chicago political machine.

“He took the loss very seriously and the it taught him a little bit about humility,” Rush said. “And I believe that it serves him well now — having a humble spirit.”

“When you are as self-assured and as confident as Barack, a loss of that magnitude … was shocking to his ego,” Rush continued. “I’m so proud of him in who he has become — the type of politician that he has become, the type of person that he has become. I think that Barack now is the best thing for America.”

But the eight-term lawmaker’s observations were not all rosy. Rush expressed concerns that Obama continues to be too “professorial” and he stressed that an Obama administration could run into serious trouble on Capitol Hill, which is expected to be teeming with conservative Democrats who may have little interest in raising taxes or nationalizing health care.

“He will really have a problem in the Congress and that’s what I’m afraid of,” Rush said. “His major obstacle would be getting his legislation passed and not just in the Senate but in the House.”

And in the unlikely event that the two ever stage a political rematch, the still-scrappy Rush said the outcome “depends on the race.”

Rush was quick to warn not to underestimate the veteran — particularly in his preferred setting. “In a local race, not a problem,” he said. “In a national race, I’ll give him that.”