Democratic presidential contender Hillary Clinton faces a crucial test in Tuesday's presidential primary in Pennsylvania. Clinton is counting on a convincing win over rival Barack Obama in Pennsylvania to keep alive her hopes of winning the White House in November. VOA National correspondent Jim Malone reports from Washington.

Clinton continues to lead in public opinion polls in Pennsylvania, but her margin over Obama has dwindled in recent weeks to single digits.

Obama was on the defensive during much of the debate they had Wednesday in Philadelphia, and Clinton is hoping to attract undecided voters who may have fresh doubts about Obama's electability.

Obama criticized the debate moderators for stirring up controversy instead of focusing on issues important to voters.

"I took us 45 minutes before we even started talking about a single issue that matters to the American people," he said.

Clinton was asked some tough questions at the debate as well. But she told a local television station in Philadelphia that she believes it is all part of the process of running for president.

"Being asked tough questions in a debate is nothing like the pressures you face inside the White House," she said. "And in fact, when the going gets tough, you cannot walk away because we are going to have some very tough decisions that we have to make, and I think we need a president who can take whatever comes your way."

A new Associated Press-Yahoo poll suggests the long and contentious Democratic primary battle may be taking a toll on both candidates.

The survey shows Democrats nationwide now believe Obama would be the stronger candidate against Republican John McCain in the November election, a shift from January when Clinton was the preferred choice.

But the poll also noted an increase in the number of voters who rate Obama as inexperienced, unethical and dishonest. Clinton fared worse, however, when rated on her likeability, honesty and ethics.

Obama continues to lead in the delegate count, and political expert Stuart Rothenberg says Clinton must stay on the attack to convince uncommitted Democratic convention delegates that she remains a viable alternative.

"She has no other option. If she does not attack, then the status quo race just continues, and that is with Obama ahead," he said. "And if she attacks, she risks a backlash, but at least there is a potential there for shaking up the race."

Some Democrats worry that the real beneficiary of the prolonged and increasingly bitter Democratic in-fighting may be the presumed Republican presidential nominee, Senator John McCain.

A recent Associated Press poll found McCain has closed the gap with both Obama and Clinton in head to head election match-ups, erasing what had been a strong Democratic advantage.