Andrew Tieng knows all he needs to know about Barack Obama: that he deeply wants the Illinois senator to be the next president.

Obama’s strategy for the economy? “I can’t really say,” Tieng admits.

Trade and tariffs? “I don’t know anything about that.”

Iraq? “I don’t know,” Tieng shrugs.

At 19, working his way through college, Tieng is the kind of voter the Obama campaign has been luring into its fold. But how they are ending up there seems based less on specifics than on a general sense that Obama’s message of change and unity is real, if somewhat amorphous.

“I don’t know why I’m for him. Something psychological, I guess,” Tien says.

That inability to explain political attraction is neither new, nor solely the province of the Obama campaign.

“It’s a difficult question to answer,” says D. Sunshine Hillygus, a professor of government at Harvard who has written extensively on voter decision-making. Hillygus says a large part of the equation is the fact that Obama is running in a primary election in which voters already inclined to support a Democratic candidate will make a choice based on a general sense of the individual, assuming there are few policy differences among the main tier selections.

In short, voters selecting Obama, a first-term senator with little voting history in Washington and who voted “present” more than 100 times in his career as an Illinois state senator, simply like the cut of his jib.

Polling suggests that Obama’s likely strength lies not with hardcore Democratic partisans but with independent voters who lean Democratic. A poll by the Rasmussen organization for the week ending Jan. 20 shows the split between Sen. Hillary Clinton and Obama.

Where Clinton attracts 44 percent of women to Obama’s 29 percent, he attracts a larger percentage of men — 35 percent to Clinton’s 32 percent. Among African Americans, a Democratic party mainstay since the New Deal, Obama attracts 62 percent.

Dick Simpson, a former Chicago alderman and now an academic, said what makes Obama unique is his capacity to inspire outside any niche. Although an African American, Obama has attracted widespread support among white voters in an otherwise polarized Chicago.

“This is an African American that they feel comfortable supporting because of what they think they understand of his personality,” Simpson said.

Charisma — something not generated by policy specifics — almost always plays some sort of role in candidate support, Simpson said, but “it may be more striking in Obama’s case.”

Clinton, he noted, has drawn support from some women less concerned about issues than the inspiration of having one of their own as a front-runner.

“You probably wouldn’t find it in her general support,” Simpson said. “To the general population she’s not as inspiring. With Obama it’s much broader. It’s not just African Americans.”

It is, in fact, people such as Kevin Sharp, a 40-year-old New Yorker who fled that city after 9/11 and settled into a pizza shop in Wicker Park, a newly fashionable neighborhood in Chicago’s north side.

Ask him about the election and he’ll announce Obama as his choice. Quiz him on policy and he’ll chortle at how little it means in the wake of the current administration, which he said was quite specific about its agenda, beginning with weapons of mass destruction in Iraq.

“The biggest lies that have been told have all been policy specifics,” Sharp says.

He likes Obama for his capacity to inspire, but has decided to vote on what he can deduce of Obama’s character as opposed to Clinton, who he fears will do little more than provide a third term for her husband, the former president.

“How much policy can you get out of someone who is young and green to the game?” Sharp says. “He’s incredibly gifted at the tongue. I don’t know that there’s been that many come out in recent years who can sell the Buick.”

Obama has almost sold the Buick to Carly Ballerini. The sale is pending while she works out some numbers from an online test she took. The quiz, making the rounds on the Internet, asks visitors a series of questions about issues important to them and then matches them with one of the candidates.

“I was all about Obama for a while. Then I took this test and found out I was really more for Hillary,” says Ballerini.

Without a pause, she adds that she finds Clinton “kind of sketchy” and is still thinking favorably toward Obama.

“I still have to go by personality,” she says. “I have to do more research.”

(Dennis B. Roddy can be reached at droddy(at)