MANCHESTER, N.H. -- Preparing to vote for the first time, Jessica Cole spent days listening to the candidates stumping for today's primary. And she's likely to make a last-minute decision when she enters the booth. "I am going to have to see," said Cole, 18, of Windham. An undeclared voter, she and many others still had not made up their minds about who they would choose one day before the nation's first presidential primary. "I have gone to see five candidates so far," Cole said. "I have listened to what they had to say about the things that concern me, like our deficit, plans for the war (in Iraq) and health care." She likes white-haired Republican Sen. John McCain of Arizona, but "I am concerned about his age," she said. "I am going to see him again today, but I probably won't decide until I walk into the booth." Elections officials said record turnout could occur because of anticipated temperatures in the 50s. Secretary of State William Gardner estimates 500,000 -- or 60 percent of New Hampshire's 830,684 registered voters -- will cast ballots. "These numbers are of historic proportions," his office said in a statement. Here, where Independents can vote along with Republicans and Democrats in the primary, the decisions made by so-called undeclared voters likely will decide the outcome. Independents represent 44 percent of the electorate; Republicans, 30 percent and Democrats, 26 percent. Cole isn't the only person likely to begin voting without having a clear choice in mind. "I will know when I walk into the voting booth, but I am 99 percent sure it will be Republican," said Eric Kilbane, an undeclared voter who owns Castro's Backroom, a cigar store in downtown Manchester with a life-sized, carved wooden statue of Cuban dictator Fidel Castro just inside the entrance. Kilbane wouldn't say which Republican he was leaning toward, "but it is definitely not Mitt Romney," a former Massachusetts governor. A weekend USA Today/Gallup poll of 778 likely Democratic New Hampshire voters showed 41 percent supporting Sen. Barack Obama of Illinois; 28 percent, Sen. Hillary Clinton of New York; and 19 percent, former senator John Edwards of North Carolina. Among 776 likely Republican voters, the poll showed 34 percent favoring McCain; 30 percent, Romney; 13 percent, former Arkansas Gov. Mike Huckabee; and 8 percent, former New York Mayor Rudy Giuliani. As campaign staffs worked to win over last-minute deciders, scores of volunteers cheerfully stood on street corners holding candidates' signs to attract the attention of passersby. "Many people just don't make up their mind until the last minute," said Matt Lebo, political science professor at New York’s Stony Brook University. "In New Hampshire, there is the problem of which primary to vote in. Independents may be making a very similar choice as they would in a general election, choosing their favorite candidate from the two parties." Lebo said Obama and McCain were doing well by "appealing to the middle of the political spectrum," and that "New Hampshire is a place where crossover appeal is very important." The outcome of voting here could determine whether all of the candidates continue, analysts said. From here, the Democratic candidates will head to Nevada to caucus and Republicans will head to Michigan for an open primary. Both parties will meet again for primaries in South Carolina -- the GOP on Jan. 19 and Democrats, on Jan. 26. "If John McCain wins in New Hampshire, then you will see Mitt Romney put up a last-ditch effort in Michigan," said John Weaver, a former chief strategist for McCain and now a GOP political consultant in Washington, D.C. "Michigan should be friendly to Romney; his father was a very popular governor there. But do not discount McCain. He has a solid existing base there." Weaver also wasn't counting out Clinton, despite her defeat by Obama in Iowa and her lower poll numbers here. "I still think she has too much national strength to be knocked out, but she is on the ropes," he said. Lebo believes Clinton's campaign is in trouble. "She will not see a victory in New Hampshire, nor South Carolina, and she may not hold on to Super-Duper Tuesday," he said, looking ahead to Feb. 5, when 24 states hold primaries and caucuses. "After (today), you will a lot of shifting with campaigns in strategy and message," Lebo said. "Voters translate these early victories into beliefs in a candidate being viable, electable, and even presidential."