Seeking an edge in the final hours, Clinton plugged her summertime gas-tax holiday proposal at every stop and released a new TV ad in both states that assailed Obama for his opposition to it. The ad called her "the candidate who is going to fight for working people."
"He is attacking Hillary's plan to give you a break on gas prices because he doesn't have one," says the ad. "Hillary wants the oil companies to pay for the gas tax this summer - so you don't have to."
Obama has accused Clinton of pandering with the proposal, and many economists are against it.
With polls showing Clinton chipping away at Obama's advantage here, both candidates darted back to North Carolina for some last-minute campaigning. It was a brief diversion from the more competitive Indiana, where each planned to return by nightfall. At stake Tuesday were 187 Democratic delegates in the two states.
"Let's listen to what the people are telling us ... because if we listen, we will hear this incredible cry," Clinton said, keeping up her populist pitch before a couple hundred people in a gymnasium at Pitt Community College.
Elsewhere, Obama campaigned among white, blue-collar workers in Evansville, Ind., before flying to North Carolina. The Democratic front-runner noted that the polls are very tight and the day's schedule had him "bouncing back and forth" between the two states.
"I want your vote. I want it badly," Obama said on a factory floor in Durham in North Carolina's high-tech Research Triangle region.
Across the two states, he focused on job losses, falling home values and soaring energy costs. He accused Clinton of practicing "me too" politics in joining Republican John McCain in calling for a temporary suspension of the federal gas tax, describing the debate as a "perfect metaphor for what's going on in Washington," an exercise in political expediency over common sense. Obama claims the tax suspensions will just encourage the energy industry to raise prices to close the gap.
Obama was trying to recover from a rough patch and put Clinton away after a difficult 16-month fight that has split the party. The former first lady, meanwhile, hoped to hang in the race with a win in one, maybe two states. Her aides lowered expectations for a victory in North Carolina, where Obama is favored, but sounded more optimistic about Indiana, where demographics seem to tilt in her direction.
Obama is ahead in the hunt for convention delegates - 1,743.5 to 1,607.5, according to an Associated Press count Monday - but Clinton senses an opening after a win in Pennsylvania last month. Still, the delegate math works to Obama's advantage, and it will be hard for Clinton to overtake him.
Nevertheless, TV ads, automatic phone calls and mailed literature flooded both Indiana and North Carolina in the run up to Tuesday while thousands of volunteers for both candidates canvassed countless neighborhoods knocking on doors. With far more cash on hand, Obama outspent Clinton by an estimated $4 million to $5 million - roughly a third more - on TV ads in both states combined.
Both candidates had punishing schedules in the final hours. Clinton was holding five events across the two states, while Obama was jetting from Indiana to North Carolina and back again over a several-hour span. Both began their day at dawn and would end it well into the night.
In the interviews, Obama and Clinton expressed confidence in their chances of winning the Tuesday contests but would not predict that voting this week would be decisive enough to end the primary fight.
On NBC's "Today" show, Obama predicted that after the final contests June 3 in Montana and South Dakota, "We will be in a position to make a decision who the Democratic nominee is going to be," he said. "I will be the Democratic nominee."
Clinton refused to predict Tuesday's results, but said her campaign has made up some ground after falling behind.
"I think we've closed the gap," she said on CNN's "American Morning."
The last-minute campaigning came as a new poll showed that most people are being squeezed by higher gas prices.
Six in 10 say gas prices have caused financial hardship for their family, including one in five who said it is causing severe problems, according to a CNN-Opinion Research Corp. poll released on Monday. That's actually a bit fewer than the number who said the cost of gasoline was hurting them a year ago.
Eight in 10 said they consider it likely they'll be paying $4 a gallon sometime this year, and more than four in 10 said they expect prices to hit $5 per gallon.