Sens. Hillary Rodham Clinton and Barack Obama began making their final appeals to voters on Sunday before the Indiana and North Carolina primaries, with Clinton sounding like a full-throated populist in highlighting her stance on the gasoline tax and Obama seizing on the issue to cast his opponent as a political opportunist.

The two Democratic presidential candidates used dueling appearances on Sunday morning talk shows, at campaign stops across Indiana, in conference calls with reporters and in an onslaught of television and radio advertisements to square off over the pocketbook concerns of voters, especially the high price of gasoline, which has become a defining issue heading into the primaries on Tuesday.

While focusing mostly on Americans' frustration with gas prices, Clinton also indirectly revived her charge — made in the approach to the Pennsylvania primary — that Obama was an elitist and unsympathetic to the economic worries of average voters. Appearing on the ABC program "This Week," she cast opposition to her plan to suspend the federal gas tax this summer as an "elite" view; while she was referring explicitly to economists' criticism of the suspension, Clinton advisers said she was also seeking to include Obama in that group because of his opposition to her plan.

Asked to name an economist who agreed with her legislation, Clinton said on "This Week," "I'm not going to put in my lot with economists." In spite of her often-professed love for empirical data, Clinton added, "Elite opinion is always on the side of doing things that really disadvantages the vast majority of Americans."

Her advisers said Clinton was increasingly sounding populist notes to portray Obama as out of touch as she sought to court working- and middle-class voters, two groups that helped her win the Pennsylvania and Ohio primaries. Obama and his team continued to push back on Sunday, deriding Clinton's gas-tax proposal as a gimmick intended to help her catch up with his lead in the national popular vote and the race to win delegates for the nomination.

"The Clinton Gas Plan isn't designed to get you through the summer, it's designed to get her through the election," read an Obama leaflet that volunteers handed out in Indiana. The message was amplified through a heavy television advertising campaign, which denounced the idea as "a bogus tax cut."

Obama campaigned door to door and at a picnic in northern Indiana, one of the most competitive regions in the state, as he also sought to end the furor over his delay of several weeks in breaking ties with the Rev. Jeremiah A. Wright Jr. after explosive comments on race and America by Wright came to light.

Appearing on "Meet the Press" on NBC, Obama said that while it was "fair" for voters to consider the matter, it had also "distracted" him and voters from the major issues in the campaign. He said he chose to finally denounce Wright last Tuesday after the pastor made more incendiary remarks.

"What really changed was a sense that he was going to double-down on the statements that he made before," Obama said. "When you are in national politics, it is always good to pull the Band-Aid off quick. Life's messy sometimes — all this stuff is happening under a spotlight and you need to deal with it quickly."

The Indiana and North Carolina primaries have emerged as major tests of political strength for both candidates: Obama wants to show the Wright matter has not chipped away at his popularity and hopes victories will help consolidate the nomination for him. Clinton is seeking to demonstrate fresh viability and seize on what has been a rough patch for Obama since he lost in Pennsylvania two weeks ago.

Clinton advisers have cast the Indiana primary in particular as a must-win for her; Obama, meanwhile, once suggested that it could be a "tie-breaker" in the Democratic nominating fight, though he backed away from that assertion on Sunday. "We have more contests remaining," he said. "I'm confident Sen. Clinton is going to stay in until the very end."

Political commercials saturated television and radio throughout the weekend, with Clinton and Obama advertisements often running back to back on local television stations. A record number of people have already voted — through Indiana's early-voting program — and election officials predict a high turnout on Tuesday in the state's first competitive Democratic presidential primary since 1968.

In some ways the candidates were a study in contrasts on the campaign trail this weekend. Clinton has seemed to be growing angrier by the day, as her political message has become a tale of working-class heroes who struggle against greedy, irresponsible villains: energy traders (who are manipulating the market in Enron-like fashion, she asserts), China (which is spying on America's businesses and poisoning its pets with tainted food), OPEC (which she will sue for antitrust violations), even the federal government (which bailed out Bear Stearns but refuses to help ordinary Americans).

"I am tired of sitting here being a patsy, of sitting here, taking it!" she cried Saturday in Gastonia, N.C., perched on the back of a vintage Chevrolet pickup.

At his campaign stops, Obama seemed to be extending an olive branch to voters who might like Clinton but were eager for the Democratic contest to end.

"For those of you who are worried about whether the Democrats are divided, you know you've got the Clinton folks and the Obama folks," Obama said. "Let me tell you something: we will be united in November. We don't want another four years of George W. Bush, and that's what John McCain is offering."

A window into the magnitude of this challenge came Sunday evening at a Democratic dinner in Indianapolis. When Clinton spoke — "I'm no shrinking violet," she declared — much of the room was silent. When Obama made his remarks, saying, "You've heard those promises before," many did not applaud.

While Obama spent the first 18 minutes on "Meet the Press" answering questions about Wright, Clinton said on "This Week" that the campaign should "definitely move on" from that controversy — even though, her advisers say privately, they are still raising the subject with party leaders and officials as they argue that she is more electable than Obama.

Clinton faced tough scrutiny herself over her plan to suspend the gas tax: One audience member, Kara Glennon, an Obama supporter, said that gas prices were "not academic" for her, given that she makes less than $25,000 a year — and then she accused Clinton of pandering.

"Call me crazy, but I listen to economists because I think I know what they studied," Glennon said.

Clinton was also questioned about her comment last month that the United States would be able to "obliterate" Iran if that nation attacked Israel with nuclear weapons. While she backed off her use of the word "obliterate" soon after she made it, she said on "This Week" that she had no "regrets" about promising a devastating attack against Iran in such an instance.

"The very idea that they would translate into action some of the most outlandish comments that have been made by some of Iran's leaders and even contemplate wiping Israel off the face of the world means that we've got to make it clear to them that that would not go without massive retaliation," she said.

Back on NBC, Obama criticized Clinton for using a word like "obliterate."

"It's not the language we need right now, and I think it's language that's reflective of George Bush," he said. "We have had a foreign policy of bluster and saber-rattling and tough talk, and in the meantime we make a series of strategic decisions that strengthen Iran."

— Jodi Kantor contributed reporting.