US Democratic presidential hopefuls Barack Obama and Hillary Clinton have held their final debate before next week's key primary in Pennsylvania.
Senator Clinton criticised her rival's recent remark that working-class voters clung to guns and religion in difficult times, calling it "offensive".
Senator Obama said the comments had been taken out of context.
Both expressed confidence that either of them could beat Republican John McCain in November's election.
But both declined to confirm whether they would ask the other to be their vice-presidential running mate.
Asked whether Mr Obama could win the presidential election, Mrs Clinton said emphatically: "Yes, yes, yes."
Senator Obama on the importance of "the biggest issues"
Mr Obama, asked the same question about Mrs Clinton's electability, responded: "Absolutely and I've said so before."
Both rivals criticised John McCain's economic plans, pledging not to raise taxes on those earning less than $200,000 a year.
The candidates' 21st debate since the beginning of the campaign came days before 158 crucial delegates will be up for grabs in Pennsylvania.
The 90-minute debate in Philadelphia gave the candidates a chance to make their case to Pennsylvania's Democratic voters.
But if Barack Obama had hoped this debate would concentrate on policy, he was disappointed, says the BBC's Jamie Coomarasamy in Philadelphia.
The first 45 minutes focused on recent gaffes, our correspondent says.
Mr Obama said he mangled his description of the mood in economically struggling small towns.
The candidates agreed they could both beat the Republican John McCain
"The problem that we have in our politics, which is fairly typical, is that you take one person's statement, if it's not properly phrased, and you just beat it to death, and that's what Senator Clinton's been doing," said the Illinois senator.
For her part, Mrs Clinton apologised for the first time for inaccurately saying she came under sniper fire in Bosnia in 1996.
Critics said she had exaggerated the dangerousness of the situation.
In another recent embarrassment, Mrs Clinton's chief strategist, Mark Penn, was forced to resign after it emerged that he had attended a meeting with Colombian officials to promote a US trade pact with the country.
Mrs Clinton has publicly opposed the policy.
Since the Democratic hopefuls last faced-off in a debate seven weeks ago, Mr Obama has come in for more criticism other than the row over his comments about small-town Americans.
He has also faced calls to distance himself from Jeremiah Wright, the pastor of his church, after clips of Mr Wright's fiery sermons were shown on the internet.
Because of the proportional system the Democrats use to distribute delegates, neither candidate will emerge from the Pennsylvania primary with much of an advantage over the other.
The latest count of pledged delegates to the party's national convention in August, according to the Associated Press, gives Mr Obama the support of 1,638 delegates and Mrs Clinton 1,502.
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