FORT WAYNE, Indiana (Reuters) - Democratic presidential candidate Barack Obama sought to convince Americans he is not elitist on Thursday as new polls showed his aura of inevitability has declined after weeks of negative headlines.

In an interview on NBC’s “Today Show,” Obama said both his rivals, Democrat Hillary Clinton and Republican John McCain, come from more privileged backgrounds than he did.

“The irony is, I think it is fair to say that both Michelle and I grew up in much less privileged circumstances than either of my two potential opponents,” said Obama.

A flap over racially charged rhetoric from his former pastor, the Rev. Jeremiah Wright, and Obama’s comments that small-town Americans “cling” to guns and religion, appears to have taken a toll on the Illinois senator as he fights for the right to face McCain in the November election.

A New York Times/CBS News poll found that 51 percent of Democratic primary voters say they expect Obama to win their party’s nomination battle against New York Sen. Clinton, down from 69 percent a month ago.

The poll said 48 percent of Democrats say he is the candidate with the best chance of defeating Arizona Sen. McCain, down from 56 percent a month ago.

Similarly, a Pew Research Center poll found a tighter national race between Obama and Clinton, with him holding a 47 percent to 45 percent lead over Clinton, down from 10 points a month ago.

“The tightening Democratic race reflects a modest but consistent decline in Obama’s personal image rather than improved impressions of Clinton,” the poll said.

Clinton, campaigning in Brownsburg, Indiana, tried to perpetuate the elitist label on Obama, pointing out his opposition to a proposal she supports, a temporary suspension of the federal tax on gasoline of 18.4 cents per gallon.

“I find it frankly a little offensive that people who don’t have to worry about filling up their gas tank or what they buy when they go to the supermarket, think that it’s somehow illegitimate to provide relief for the millions and millions of Americans who are on the brink of losing their jobs, unable to keep up with their daily expenses,” she said.

Still, Obama picked up an important endorsement in Indiana when former Democratic National Committee Chairman Joe Andrew announced he was switching support from Clinton to back Obama.

Andrew, DNC chairman when Bill Clinton was president, is a so-called superdelegate to the party’s nominating convention this summer and as such can vote for the candidate of his choosing. With Obama holding a small lead over Clinton in the race for committed delegates, superdelegates may ultimately decide the Democratic nominee.

Indiana is one of two states, along with North Carolina, holding nominating contests on Tuesday that could have an impact on the race if either candidate wins both of them.

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Andrew said in a long letter explaining his switch that it was time to “heal the rift in our party,” end the lengthy nominating process and pick a candidate to face McCain.

“While I was hopeful that a long, contested primary season would invigorate our party, the polls show that the tone and temperature of the race is now hurting us,” Andrew wrote.

The Clinton campaign found reason for optimism from a Quinnipiac University poll that showed Clinton topping McCain in a hypothetical matchup in the battleground states of Florida, Ohio and Pennsylvania.

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Clinton led McCain in those states from margins ranging from 8 points in Florida to 10 in Ohio and 14 in Pennsylvania, the poll found. Obama beat McCain in Pennsylvania but was in a virtual tie with him in the other two states.

Democrats tried to use against McCain the fifth anniversary of Bush’s speech declaring an end to major combat operations in Iraq, an event quickly followed by a rising Iraqi insurgency that has kept U.S. forces in Iraq to the frustration of Americans.

McCain, in Cleveland, defended his support for the current strategy in Iraq while denouncing the White House for putting a “Mission Accomplished” banner behind Bush on the USS Abraham Lincoln on May 1, 2003.

“I thought it was wrong at the time. I thought phrases like ‘a few dead enders,’ ‘last throes,’ all of those comments contributed over time to the frustration and sorrow of Americans,” he told reporters.

There was good and bad for McCain in a Wall Street Journal/NBC News poll.

He was in a statistical dead heat with both Obama and Clinton, but the survey said overall support for Republicans in general had fallen and that 43 percent of Americans have “major concerns” that McCain will be too closely aligned with the agenda of President George W. Bush.

(Additional reporting by Andy Sullivan and John Whitesides, Writing by Steve Holland; editing by David Alexander)