CONCORD, N.H. -- His voice hoarse but sturdy after 11 months of campaigning, Sen. Barack Obama yesterday asked a crowd in the Concord High School gymnasium for a show of hands -- who still hasn't picked a candidate?

Several hundred people, nearly a third of the attendees, threw their arms in the air, just four days before Tuesday's New Hampshire primary.

"I am going to try to be so persuasive in the next 20 minutes," the Illinois Democrat, fresh from his Iowa caucuses win, told the group, "you will say to yourself, 'I must vote for Obama on Tuesday.' Now that we have you in our sights, we're coming after you."

About 35 miles south, in Hudson, Arizona Republican Sen. John McCain was making a similar pitch to the state's "undeclared" voters -- those who can vote in the Republican or the Democratic presidential primary and quickly alter either party's political calculus.

Of those voters who chose the GOP primary in 2000, 61 percent supported Mr. McCain. This time, Mr. Obama is the fresh face. A Reuters/C-SPAN/Zogby poll released yesterday found at least 60 percent of New Hampshire independents planning to vote in the Democratic primary.

"It's your birthright in New Hampshire to meet all the candidates," said Kent Ruesswick, 54, an independent who has always voted in GOP primaries but now is distressed by the Republican Bush administration's deficit spending. "This time, I'm going to vote for a Democrat."

Overall in the Reuters poll, New York Sen. Hillary Rodham Clinton led Mr. Obama, 32 to 26 percent, while Mr. McCain led former Massachusetts Gov. Mitt Romney 34 to 30 percent. But both parties have undecided voters: 7 percent for Republicans, and 8 percent for Democrats.

Independents make up more than 40 percent of New Hampshire registered voters. According to a Jan. 2 CNN/WMUR poll, Mr. Obama has steady led Mrs. Clinton among those voters over the past month.

Paul Manuel, executive director of the New Hampshire Institute of Politics at Saint Anselm College, predicted a possible post-Iowa surge for Mr. Obama, the first black candidate to win the caucuses. "The enthusiasm might bring people out to vote," he said. "There might be a gravitational pull toward him."

That could leave a much smaller pool of independents for Mr. McCain. "McCain is fighting a little bit of a two-front war in New Hampshire," said state Republican Party Chairman Fergus Cullen. "He's fighting Romney and Obama."

Mr. Cullen said the perceived institutional favorites, Mr. Romney and Mrs. Clinton, can't appeal to independents as easily as Mr. McCain and Mr. Obama can. "I think both are viewed as not being part of the conventional establishment," he said.

At least, that's an image both men eagerly put forward.

Mr. McCain, despite his long Washington tenure, touts his wartime experience and many years crossing party lines or bucking GOP leaders. He has attracted a range of backers, from the conservative Union Leader newspaper to the left-leaning editorial page of The Boston Globe. Connecticut Sen. Joe Lieberman, now an independent but the Democrats' vice presidential nominee in 2000, has been campaigning here for the Arizona Republican.

"I'm running for president because I think we've got to restore trust and confidence in government," Mr. McCain said last night at a packed VFW post. "I'm a proud conservative, but we Republicans betrayed our base when we let spending get completely out of control."

He reminded the crowd that he has been critical of the Bush administration's conduct of the Iraq war, but he has also been unwilling to pull out troops. To the contrary, he called for a larger military force there before the president decided to commit nearly 30,000 more troops last year, leading to a significant drop in violence.

Several audience members were eager to remind Mr. McCain, a former Navy pilot, that they respect his military service, including as a Vietnam War prisoner in Hanoi.

"That's when I really learned to love America," he said. "I was privileged to serve in the company of heroes."

Undeclared voters like Jim Mudge, 52, who voted for Mr. McCain in 2000, were well represented at the event. He said there's a small chance he could support Mr. Obama, whom he planned to see today. But he's discouraged by Mr. Obama's scant foreign policy experience.

That's a line of criticism some Democrats, including Mrs. Clinton, have used consistently against Mr. Obama. But yesterday in Concord, he touted his limited Washington years as a plus, and echoed Mr. McCain's promise of "straight talk."

(Mr. McCain is traveling across New Hampshire on the "Straight Talk Express" bus, just as he did eight years ago.)

"We have a chance to pull Democrats and Republicans and independents together, and stand up once and for all and say we are one nation, we are one people, and our time for change has come," Mr. Obama said. "We have a chance to move beyond the bitterness, the partisanship, the anger that has characterized Washington for so long."

The crowd roared.

"It was awesome," said college student Max Nichols, 20. "He's a great speaker. He's charismatic, something we've been missing over the past few years."

Mr. Nichols is one of the state's tens of thousands of new potential voters, including more than 200,000 who arrived between 2001 and 2006. (New Hampshire allows Election Day registration.)

In Iowa, Mr. Obama proved his popularity with new and young voters, winning support from 57 percent of caucus-goers under age 29 and 41 percent of first-time participants, according to a CNN entrance poll.

"If they elect another Clinton or a Bush, I'm moving to Canada," said undeclared Marybeth Fairhurst of Concord. "I think we can use some new blood."