Philadelphia, April 20: Acrimonious exchanges between Democratic presidential hopefuls Barack Obama and Hillary Clinton heightened as they launched an intense last minute campaign for the crucial Pennsylvania primary on Tuesday in a bid to win undecided voters and influence those in the opposite camp.

In a sharp personal attack, Obama branded Clinton's tactics as "slash and burn" and asserted that she said what people want to hear. The former first lady struck back, asking voters to look beyond Obama's speech-making.

Clinton -- still leading in the opinion polls though by a small margin in the State where she needs to make a strong showing -- claimed that Obama would be unable to deal with the problems facing the nation or deliver on his promises. Analysts say the fight between Obama and Clinton is expected to play out until the Democratic convention in Denver in August, where the party candidate would be finally endorsed irrespective of who wins and by what margin in the State.

To the chagrin of the party bosses, the campaign in the closing days has been marred by personal attacks with the substantial issues taking a back seat.

In a dramatic move, Obama boarded a rail car for a four-day whistle stop final campaign which is expected to give him opportunity to talk to the voters in the small towns, some of whom might have been annoyed by his remarks that people in small towns cling to guns and religion in the times of economic adversity.