Sen. Barack Obama has his work cut out to gain the backing of Sen. Hillary Clinton's diehard supporters. That will be an important task this week for the Democratic convention.

A recent poll shows that fewer than half of Sen. Clinton's supporters in the presidential primaries plan to vote for Mr. Obama, the presumed Democratic presidential nominee.

The USA Today/Gallup Poll taken Thursday through Saturday found that 47 percent of Sen. Clinton's supporters are firmly behind Sen. Obama. Twenty-three percent say they support him but may change their minds before the election.

Then there are 30 percent who say they will vote for Republican John McCain, someone else or no one at all.

New York Sen. Clinton is supposed to address the convention tonight; what she says will be important to ensure party unity. And her name will be placed in nomination. How she handles the convention will be crucial.

Mr. Obama will need the undivided support of his party to win the election. Several polls show a tight race between Sen. Obama and Arizona Sen. John McCain, the presumed Republican nominee.

The USA Today poll shows Mr. Obama with a 47 percent to 43 percent lead among registered voters and a 48 percent to 45 percent edge among likely voters. Both are within the margin of error of 4 percentage points.

In the last poll taken a month ago, Sen. Obama led Sen. McCain by 3 percentage points, but Mr. McCain led by 4 points among likely voters.

Perceived lack of experience is Sen. Obama's chief weakness: 57 percent of respondents are concerned about that while 44 percent question whether he could be an effective commander in chief. Although voters prefer his chances at handling the economy over Sen. McCain, they believe the Democrat will raise their federal income taxes if elected.

The poll shows voters regard Sen. McCain as a strong and decisive leader. But they doubt his ability to handle the economy and worry that his economic policies would benefit only the wealthy.

Eight of 10 voters are dissatisfied with the country's current direction. That places more of a burden on Sen. McCain to show he can turn things around, and favors Sen. Obama — if he can get his party behind him.