"People are a little more familiar with me in Indiana," says the senator from next-door Illinois, claiming a better chance than he had in Pennsylvania, wherebeat him convincingly last week.
It's a view that runs counter to the conventional wisdom, which holds that Indiana is a Rust Belt rematch, advantage Clinton following her victories in other states with large numbers of blue-collar voters.
Before the first speech or TV commercial here, both campaigns sized up Republican-red Indiana as naturally more competitive than Pennsylvania or any other late Democratic presidential primary, including North Carolina, which also votes next week.
As a result, they each see a potential turning point, the front-running Obama eager to wrap up the nomination and Clinton determined to keep her candidacy alive with a strong run through the spring contests.
Compared with Pennsylvania, there are differences in geography, age, religion and rules that permit independents to vote, each of which figures to benefit Obama. Yet Indiana is more rural, and Clinton has the support of Sen. Evan Bayh, the state's pre-eminent Democrat. It is home to a significant blue-collar population, and a spirited gubernatorial primary with a woman on the ballot may help raise turnout among female voters who prefer the former first lady.
"When you do the tote board, there are intangibles that work for Clinton, there are intangibles that work for Obama," says Fred Yang, a pollster working on the gubernatorial primary.
Proximity to Obama's home state matters, according to both campaigns.
"Indiana borders Illinois and shares media markets, which is a huge help to Senator Obama," said Howard Wolfson, a top strategist for Clinton. "He has not yet lost a state that borders Illinois."
Roughly 20 percent or so of the primary electorate lives within reach of Chicago television stations, meaning that thousands of potential voters have been watching Obama in their homes since his successful 2004 Senate election campaign. The part of Indiana nearest Chicago also is home to large numbers of blacks, likely to support Obama overwhelmingly.
Independents and Republicans are allowed to vote in the Democratic primary in Indiana, a change from the Democrats-only rules that applied in Pennsylvania.
That's presumably good news for Obama, who has outpolled Clinton among independents in the contests to date by a combined 55-39 percent.
Then, too, the population in Indiana is significantly younger than in Pennsylvania.
In Indiana, 12.4 percent of all residents were age 65 or older in 2006, according to Census Bureau statistics. In Pennsylvania, where it was 15.2 percent, those voters cast 22 percent of all ballots in the April 22 primary, a total that reflected a well-established tendency of seniors to vote in disproportionately high numbers. Clinton won 63 percent of their votes.
"Demographically, the biggest difference is that that there's a lower Catholic vote compared to Pennsylvania," said Geoff Garin, Clinton's top strategist. "And as well as she's been doing with older people and blue collar voters, our best group on a pretty consistent basis has been Catholics."
Catholics accounted for slightly more than a third of the votes cast in the Pennsylvania primary. Clinton won their support overwhelmingly, but split the Protestant vote with Obama.
Garin estimated Catholics will cast roughly 20 percent of the Indiana ballots.
Pete Brodnitz, a pollster working in the gubernatorial race, agreed, and said Protestants likely will cast more than twice as many votes as Catholics in Indiana.
Garin and Yang are at the same firm, and Brodnitz and Joel Benenson, an Obama pollster, are partners. Both pairs say they keep their work separated.
Obama isn't contending this time with a popular governor and mayor, as was the case in Pennsylvania.
Gov. Ed Rendell, together with Philadelphia Mayor Michael Nutter, held down Obama's share of the vote in Philadelphia. The governor won 78 percent of the citywide vote in a gubernatorial primary six years ago, and 85 percent in the Philadelphia suburbs. Obama got 65 percent and 48 percent.
In Indiana, Gov. Mitch Daniels and Indianapolis Mayor Greg Ballard are both Republicans.
But other factors favor Clinton.
She long ago won the support of Bayh, the state's dominant Democrat, and he has campaigned energetically with her.
Then, too, the 2000 Census found that 29 percent of Hoosiers live in rural areas, considerably higher than the 23 percent in Pennsylvania, and that means a large conservative population, even in a Democratic primary. That ought to be good news for Clinton, who won more than 60 percent of the rural vote in the last primary.
Indiana also is marginally more white than Pennsylvania, and its residents are slightly less well educated, according to the Census Bureau. More good news for the former first lady, based on earlier primaries.
Then there's the gubernatorial primary between Jill Long Thompson and Jim Schellinger, a close race that may give women a stronger-than-usual incentive to vote than in Pennsylvania. As the strongest female presidential candidate in history, Clinton has consistently outpolled Obama among women.
Finally, there is an unknown impact of a Republican-crafted state law requiring voters to show a photo identification before they are given ballots. Democratic critics have long claimed it presents an unconstitutional barrier to voting, but the Supreme Court upheld the measure earlier this week.
Impact on a competitive Democratic primary? Unknown.