Manchester, N.H. – Former President Bill Clinton stepped up attacks on Vermont Sen. Bernie Sanders at a rally Monday, emerging as his wife Hillary's fiercest advocate a day ahead of New Hampshire's primary vote.

“It bothers me to be in an election where a debate is impossible because if you disagree you are just part of the establishment,” he said, arguing that the "mythical establishment" should not be the enemy.

“The real question is not whether or not we need big changes,” he added. “The real question is who will be the change-maker.”

Bill Clinton's comments were part of an increasingly sharp attack on Sanders, whose anti-establishment critique has propelled him to a double-digit lead in the New Hampshire polls.

It also reflects a changing strategy for the ex-president, who until recent days has played a largely understated role in this campaign after earning damaging headlines in 2008 for calling Barack Obama's election platform a "fairy tale."

The Clinton campaign isn't banking on a win here, but instead it's hoping to boost support among younger voters ahead of primaries on what should be friendlier turf in the South. Even though the former secretary of state notched a narrow victory last week in Iowa's caucuses, exit polls showed younger voters overwhelmingly supported the Vermont senator.

At a rally at Manchester Community College that attracted an overflow crowd, Clinton urged the skeptics to give her a second look.

“For those of you who are still shopping, I hope I can close the deal,” she said. “You may not support me now, but I will always support you.”

New Hampshire holds important symbolism to the Clintons. It was here in 1992 where Bill Clinton declared himself the "comeback kid" after a surprising second-place finish, and his wife won a major victory in New Hampshire in 2008 after losing Iowa to Obama.

"New Hampshire means a lot to us, going all the way back to 1992. It gave us a chance to head out of here with momentum on the way to the nomination," she said. "And we’ve never forgotten that."

Yet the odds are long for a repeat here. Sanders, who lives next-door, has attracted raucous crowds at his own rallies, where supporters trumpet his plan for free college tuition and a "massive" federal jobs program.

"I have a lot of friends who support him," said Olivia Marr, among the students in Clinton's crowd. "He has a lot of radical ideas and he's very, very progressive. But her experience is what gets me. And her intelligence. She has a plan, she has an agenda, and she's willing to attack it head on."