June 27 (Bloomberg) -- The first year Barack Obama joined his fellow Illinois state senators for their annual golf game, he was less than impressive.

``He just wasn't good,'' said State Senator Donne Trotter of Chicago, adding that the yearly golf outing of the legislature's black caucus is a social-networking rite of passage, particularly for politically ambitious newcomers.

In 1998, the following year, Obama showed up and surprised colleagues by hitting the longest ball, according to Trotter, a onetime political foe who now backs Obama, a U.S. senator from Illinois and presumptive Democratic presidential nominee.

``He took lessons during the winter,'' said Trotter, 58. ``That's the same way he addresses the more important things in life -- always preparing himself for the next level.''

Obama, who grew up in laid-back Hawaii, cultivates an image of cool. Yet friends and colleagues said his unflappable demeanor masks a competitive streak that fueled his ascent from average student to Harvard Law Review president to state lawmaker to Congress and possibly the White House.

Obama, 46, examined this drive in his 2006 book ``The Audacity of Hope.''

`Sharp Elbows'

``I understand politics as a full-contact sport, and minded neither the sharp elbows nor the occasional blind-side hit,'' Obama wrote about his early political life.

His decision to run for the U.S. Senate in 2004 followed the defeat of his 2000 bid for an Illinois U.S. House seat against incumbent Bobby Rush -- a setback compounded by having a wife weary of political life and consultants advising against a run.

``He lost but rebounded fast and put himself out there to run for the U.S. Senate,'' Trotter said in an interview. ``There were millionaires, people with much bigger name recognition, who were in the running, but you can't win if you don't play, and he's always made himself a player.''

That spirit was evident at an early age on the basketball court. In his 2004 memoir, ``Dreams from My Father,'' Obama describes his early love for the sport even with ``limited talent.''

High-School Basketball

He wasn't the strongest player at Honolulu's prestigious Punahou School, though he was one of the most determined, according to former teammate Alan Lum. On a scale of one to 10, Obama is a clear ``10'' when it comes to competitiveness, Lum said, adding that he didn't shy away from calling out his teammates when they weren't pulling their weight.

``He wasn't going to let anybody get away with anything -- that was his game,'' Lum said.

Senator Bob Casey, a Pennsylvania Democrat, got a taste of Obama's competitiveness while helping him campaign in his state's primary in March. The two played each other in several early- morning games.

``Unfortunately for me, he's more than competitive,'' said Casey, 48.

Obama's drive doesn't only extend to fellow senators. In Indiana last month, he was challenged to play basketball by a 14- year-old boy, Aaron Villicana. The two played PIG, a game of elimination in which a player earns a letter for failing to make a basket.

`Finish You Off'

``I'm going to finish you off right here,'' Obama said during the prolonged game, right before missing a basket. He ultimately won.

The candidate and his aides like to emphasize the presidential contender's cool-under-fire image. In March, at the height of the Democratic nomination battle against Senator Hillary Clinton of New York, Obama adviser Merrill McPeak, a retired general and former Air Force chief of staff, dubbed his candidate ``No Shock Barack'' and ``No Drama Obama.''

Obama often talks up his steady nature. ``I don't get too high, I don't get too low,'' Obama told CBS's ``60 Minutes'' in February.

Supporters and opponents alike have speculated whether Obama's even keel amounted to potential weakness as Clinton, 60, and the presumptive Republican nominee, Arizona Senator John McCain, 71, stepped up their attacks on the less politically experienced Obama during the primary season.

Such concerns, longtime friends said, are unfounded and don't take into account Obama's fervent drive to prevail, whether in his quest for the highest office, on the basketball court, or in a rural Pennsylvania bowling alley, where, in March, after several gutter balls, he stayed longer than expected and even solicited tips from a 8-year-old boy.

`Competitive Spirit'

``Barack does not like to lose,'' Valerie Jarrett, a senior adviser and friend, said in an April interview. ``He's really competitive, he has a fierce competitive spirit.''

Obama has acknowledged as much. In early March, reflecting on 11 consecutive caucus and primary wins, he said his fighting spirit was triggered when he was defeated by Clinton in the Jan. 8 New Hampshire primary.

That setback was a lesson that ``this is not going to come easy,'' he said. ``We are going to have to earn this victory.''

This trait also applies to more mundane contests. On a May 9 flight from Washington to Portland, Oregon, he played the word game ``Taboo'' with reporters on his campaign plane.

The senator was vigilant about keeping score and taunted the reporters.

``And you guys are the wordsmiths,'' Obama jeered after his victory.

To contact the reporters on this story: Kim Chipman in Washington at kchipman@bloomberg.net; Julianna Goldman in Washington at jgoldman6@bloomberg.net.

Last Updated: June 27, 2008 00:01 EDT