Some new public opinion polls suggest a close and volatile presidential race in the months ahead. VOA National correspondent Jim Malone has more from Washington.
Some good news for Hillary Clinton in her battle with Barack Obama for the Democratic Party's presidential nomination.
The latest Gallup poll has Clinton pulling ahead of Obama by a margin of 49 to 42 percent.
But there was also good news for the presumed Republican presidential nominee, Senator John McCain. The latest Reuters-Zogby poll shows McCain beating Obama by a margin of 46 to 40 percent, and defeating Clinton by a margin of 48 to 40 percent.
McCain was in Britain Thursday as part of a congressional trip to Europe and the Middle East.
After a meeting with Prime Minister Gordon Brown, McCain said he appreciated British military efforts in Iraq.
"All I can do is express my gratitude to the British government and people, and especially the brave young people who are serving," said McCain.
McCain has made victory in Iraq the centerpiece of his presidential campaign, and has criticized Democrats Clinton and Obama for advocating a gradual withdrawal of U.S. troops from Iraq.
Obama took his presidential campaign to West Virginia where he said the half trillion dollar cost of the Iraq war was a drag on the U.S. economy.
Obama also criticized McCain for embracing President Bush's policies on Iraq and the economy.
"No matter what the costs, no matter what the consequences, John McCain seems determined to carry out a third Bush term," said Barack Obama. "That is an outcome America cannot afford."
Recent polls suggest about 60 percent of Americans still view the Iraq war as a mistake. But a growing number of voters now see the military surge strategy in Iraq as a success and believe McCain might be the candidate best able to handle the situation in Iraq.
Karlyn Bowman monitors U.S. public opinion.
"The war, at least at this stage, is not the albatross that many people predicted it would be for the Republican candidate," said Karlyn Bowman.
McCain has the luxury of having his nomination battle wrapped up. That is not the case for Obama and Clinton as they look ahead to the Pennsylvania primary on April 22.
Senator Clinton is hoping to cut into Obama's lead in the delegate count with a victory in Pennsylvania, and is also hoping for re-votes in the large states of Florida and Michigan.
"So again, I would call on Senator Obama to join me in supporting the rights of the people of Michigan and Florida to have their voices and their votes counted," said Hillary Clinton.
Florida and Michigan held primaries in January that Clinton won. But the national Democratic Party disallowed the results because the two states moved up the dates of their primaries in violation of party rules.
Clinton is hoping that re-votes of the two primaries would give her new momentum and added delegates in her battle with Obama. But it now appears unlikely that state party officials in both states will be able to agree on holding either a new primary or a mail-in vote.
Political analysts say redoing the Florida and Michigan votes is a key part of Clinton's strategy to win the Democratic nomination.
John Fortier is a political expert at the American Enterprise Institute in Washington.
"She really needed not only the delegates, but the momentum and the possibility of more delegates out there to keep her campaign going," said John Fortier. "And as it looks like that is not going to happen, the odds of her winning the nomination are very, very small. The delegates are not there, the momentum is not there, and because of that you may see some super delegates coming to that conclusion in the next few weeks before Pennsylvania."
Super delegates are uncommitted party activists and elected officials who will play a crucial role in choosing the Democratic party nominee for president. Neither Obama nor Clinton can win enough delegates in the remaining primaries or caucuses to secure the nomination outright, so both candidates are making a play for their support.