Illinois Sen. Barack Obama showed this morning why he’s in the presidential race with his best debate performance to date, one in which he commanded details, looked Oval Office ready and effectively made the case that he is indeed the candidate of true change — and that instead of polarizing GOP voters in the fall of 2008 he may be able to pick off some of them.

Obama gained the most ground of any of the candidates in the debate.

This was Obama’s morning in large part because he exceeded expectations after having lackluster days on the stage in previous debates. Those of us in Iowa, out on the campaign trail, saw more of the Obama that has energized and even electrified some crowds.

Want a change? “I’m your guy,” said Obama.

“We’re going to need someone to break out of the political pattern we’ve been in the last 20 years,” Obama said.Seen through an Iowa lens, Obama pulled points for talking about capping subsidies to large ag-business to help the family farm. His was the most specific agriculture answer.

Obama flipped the script on  an early debate attack on his foreign policy posturing with a folksy one-liner, joking that he had prepared for the Drake University-hosted ABC News debate by riding in bumper cars at the Iowa State Fair. He then noted that he had the “strength” to go toe-to-toe with dictactors — a nice finessing of criticism of his alleged lack of experience in foreign policy.

Hillary Clinton filed another strong performance, but the boys caught up to her. The Grand Dame of the Democratic slate didn’t own the stage as she had in past debates. But she did what she needed and earned points with her final answer, noting that the women’s movement is responsible for her being taken seriously as a candidate. She also struck just the right note with a line about her mother: that she wasn’t able to go to college (it goes without saying this is the result of regimented gender roles) and that Hillary is doing what her mom couldn’t. This reference to her mother resonates in traditional Iowa, where women (who have never had one of their own in the U.S. Senate or Congress or governor’s office) don’t want to be high-hatted, but can relate to Clinton’s mom — and may just catch a glimpse of the goals they had for their daughters in her campaign.

Like Obama, Hillary effectively parried a line of questioning about her potential polarization of the electorate. When shown a quote from Bush puppet-master Karl Rove about Hillary’s high negatives, she responded by saying that the Bushies seem “obsessed” with her (which is true) and that the reason is: “We’ve taken them on beaten them.”

No Democrat, she noted, is going to escape the GOP political attack machine, and the Clinton counter-attack capability is a proven mechanism. “I know how to beat them, so yes, they’re going to be driving up negatives.”

This was also Bill Richardson’s best showing in the debate. He made a case to voters that they could split the difference between Obama (freshness) and Clinton (trusted hand) by voting for him, the Hispanic governor of New Mexico with a king’s ransom of foreign policy experience. “With me, you get both,” Richardson said.

Richardson had by far the best response on education issues, saying that “teachers are disrespected” and No Child Left Behind should be scrapped. Others have made these points, but Richardson reaches the heart of educators — a significant force in the Democratic Party — by going “Mr. Hollard’s Opus” on them in calling for arts and music to be increased in the schools. That line alone should do wonders with him among Iowa educators, as it is as much a symbolic answer as it is substantive.

Edwards had a good morning as well — showing that the race in Iowa is a battle of four. He didn’t throw any haymakers, but Edwards, in that easy North Carolina mill worker son way of his, with the John Grisham novel character appeal, was the first to use the words “hope and optimism” and talked of the Democratic Party being the party of the people and refusing campaign money from the insurance industry and Big Pharma. That’s the real reason we have don’t have a universal health-care system, Edwards reasoned. He makes a strong case that if your overarching issue as a voter is corporate America versus the Working Man that he’s your man for the fight.

As far as the other candidates, Sens. Joseph Biden and Chris Dodd look like what they are: estimable senators who in any other year, with a different field, may have more traction.

Dennis Kucinich seems starved for attention. It’s pathetic. He should spend his weekends with his youthful-looking wife, who the ABC cameras panned to several times.

And Mike Gravel … He’s even wearing out his welcome with political junkies who set their alarms for 7 a.m. today so as not to miss out on any of the action. I interviewed him for 45 minutes one Friday afternoon and, frankly, this 76-year-old already has had more than his day in court. It’s time for him to free up time for the others as this race could be getting awfully close in Iowa.