Clinton took the debate dispute to a new level, challenging Obama to face off with her in a debate without a moderator.
"Just the two of us, going for 90 minutes, asking and answering questions, we'll set whatever rules seem fair," Clinton said while campaigning in South Bend.
Her campaign made the offer formal with a letter to the Obama campaign. Obama aides said they were studying the letter.
Trailing in delegates and the popular vote, Clinton has been stepping up the pressure on Obama for more debates in advance of primaries in nine days in Indiana and North Carolina. Clinton argued that Obama won't debate because he's unhappy with questions from TV moderators during the April 16 debate just before the Pennsylvania primary. After that debate, Obama complained it focused too much on political trivia and too little on real issues.
On the campaign trail Saturday, he sounded much the same theme.
"I was convinced that the American people were tired of the politics that's all about tearing each other down. The American people were tired of spin and PR, they wanted straight talk and honesty from their elected officials," Obama said at a town hall meeting in the aging industrial city of Anderson.
"If you watched the last few weeks of this campaign, you'd think that all politics is about is negative ads and bickering and arguing, gaffes and sideline issues," said Obama. "There's no serious discussion about how to bring jobs back, to Anderson."
Both rivals were focusing on Indiana on Saturday, with Clinton bringing along popular Sen. Evan Bayh and talking about reviving the industrial economy.
"We can do that again, but we need, as Senator Bayh said, a president who doesn't just talk about it but who actually rolls up her sleeves and gets to work," said Clinton.
The two Democratic candidates were stumping in the heart of Republican territory, and Obama sought to reach across party lines, saying he has struggled to avoid the back-and-forth bickering of the campaign, and focus on issues like plant closings that have damaged cities like Anderson.
"I've been trying to resist that in this campaign and I will continue to resist it when I'm president of the United States," said Obama.
Clinton was focused in eastern Indiana along the Ohio border in industrial pockets as well, seeking to build a coalition of working-class voters similar to the one that served her well in neighboring Ohio.
The next round of primaries in the historic contest for the Democratic nomination comes May 6 when Democrats in Indiana and North Carolina go to the polls. Obama is favored in North Carolina, but the polls have shown the race in Indiana far too close to call.
The North Carolina primary offers 115 national convention delegates, the largest prize among the nine contests remaining. Indiana has with 72 delegates available.
In the overall race for the Democratic Party nomination, Obama leads with 1,724.5 delegates, including superdelegates - unelected party officials who can vote as they please. Clinton had 1,593.5, according to an Associated Press tally. It takes 2,025 to win the nomination.
With no end in sight soon for the Democratic contest, Obama sought to ease worries that the intraparty fight will leave the party vulnerable in November.
"Everybody is kind of nervous about this Democratic primary, it's been going on a long time," said Obama. "I have my differences with Senator Clinton and she has her differences with me. We will be united in November and beat John McCain and the Republicans."
Obama also underscored his differences with McCain, the certain Republican nominee.
"John McCain says he's different, but when you look at his policies he's got no agenda for you, how to make you a little more successful," Obama told his heavily blue-collar audience. "We know in our hearts that this country is not going down the right track, something needs to change right now and that's what's at stake in this election."
In Anderson, Obama noted that McCain has switched views on issues like tax cuts for the rich to curry favor with the conservative Republican Party base. "The straight talk express lost a wheel," said Obama.
McCain's campaign was quick to respond. "This again shows that Barack Obama doesn't understand the economy. Americans are looking for proof that the next president is going to be someone who understands their needs," McCain spokesman Tucker Bounds said in a statement.