DURHAM, N.H. -- Republican presidential candidate Sen. John McCain has built a slight lead over Democratic candidate Sen. Barack Obama in the latest New Hampshire poll.

Link: New Hampshire Poll Results

The WMUR/Granite State Poll conducted by the University of New Hampshire Survey Center shows that 47 percent of likely voters plan to vote for McCain, with 45 percent saying they plan to vote for Obama.

The poll of 523 likely voters was conducted From Sept. 14 to Sept. 21 and has a margin of sampling error of 4.3 percent.

McCain's narrow lead is within the margin of error, and many of the voters in the survey indicated that they were not yet completely committed to their choice.

The poll indicates that 38 percent of voters said they firmly support Obama, 5 percent said they support Obama but could change their minds, and 3 percent are undecided but leaning toward Obama.

The numbers are similar with McCain: 37 percent say they firmly support McCain, 5 percent say they support McCain but could change their minds, and 5 percent are undecided but leaning toward McCain.

Pollsters asked half the voters whom they would vote for if the election were held today, and the other half were asked whom they plan to vote for looking ahead to the November election. Among those who were given the more immediate timeframe, 8 percent were undecided, but among those given the longer timeframe, 20 percent were undecided.

"The race in New Hampshire is very close, but about 1 in 4 voters are not firm in supporting either candidate," said Andrew Smith, director of the UNH Survey Center. "New Hampshire is definitely a state that is up for grabs and will remain so until Election Day."

McCain has taken the lead among independent voters, with 41 percent of independents saying they support McCain, compared to 35 percent supporting Obama. McCain holds a 53 percent to 40 percent lead among men, while Obama holds a 50 percent to 42 percent lead among women.

Among voters who chose Sen. Hillary Rodham Clinton in the primary, 14 percent said they plan to vote for McCain, while another 10 percent said they are undecided.

While voters are split between Obama and McCain, both have solid favorability ratings. Obama's net favorability -- the percentage of voters who have a favorable opinion of him minus the percentage who have an unfavorable opinion -- is +17 percent, down from +27 percent in July.

McCain's net favorability is +20 percent, down from +25 percent in July. Among independents, Obama has a +30 percent favorability and McCain has a +36 percent favorability.

Vice Presidential Favorability

The vice presidential candidates both have a +13 percent net favorability. Democratic Sen. Joe Biden is viewed favorably by 45 percent of voters and unfavorably by 32 percent.

Alaska Gov. Sarah Palin is viewed favorably by 48 percent of voters and unfavorably by 35 percent.

The poll indicates that Palin has energized Republican voters more than Biden has energized Democrats. Among Republicans, Palin's net favorability is +78 percent, while Biden's net favorability among Democrats is +61 percent.

But voters are split on whether the choice of Palin makes them more likely to vote for McCain. Twenty-eight percent of likely voters said she has made them more likely to vote for McCain, and 26 percent said they are now less likely to vote for him, with 45 percent saying it makes no difference.

"She has served as a catalyst in this campaign," Smith said. "She isn't a major factor in determining who people are going to vote for, but she's changed the dynamic of this campaign and energized Republicans."

In what is expected to be a close nationwide race, New Hampshire's four electoral votes are being sought by both candidates.

The economy is far and away the most important issue in the election, according to the poll. The economy has been the top issue since April, and it has risen from the top choice of 41 percent of voters to 47 percent in the latest poll.

The war on terrorism was the next most important issue, with 11 percent, followed by the war in Iraq, with 10 percent. Concern over gas prices fell to 7 percent from a high of 13 percent in July.

Democrats expressed more concern about the economy than Republicans, while Republicans showed more concern about terrorism.