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President Barack Obama scooped up campaign cash in his Chicago hometown on Wednesday, promising supporters that change can still come if they work even harder this time around.

A day after former Massachusetts Gov. Mitt Romney's convincing win in New Hampshire's GOP primary, which established him as the clear front-runner to take on the president in the fall, Obama's visit home was all about summoning his backers' enthusiasm for the fight ahead -- along with reminders of what he left behind four years ago.

"If you're willing to work even harder in this election than you did in the last election, I promise you, change will come," Obama said at a large fundraising event at the University of Illinois at Chicago.

"You can't back down -- not now. We won't give up -- not now," Obama said. "We've got to send a message we are going to keep pushing and fighting for the change that we believe in."

Obama used the trip to restock his re-election finances while making a surprise visit to his campaign headquarters for the first time. A few hundred staffers listened as Obama reminisced about the early days of his Senate campaign and thanked campaign aides for their hard work. But publicly, the president was beginning to offer a contrast with Romney.

Obama's team has castigated Romney at every turn as a political opportunist willing to alter his views -- on abortion, the environment and gay marriage -- to serve his political purpose.

Without naming Romney, Obama said he had led an administration of principle that has tried to invigorate the economy and kept its promises.

"I'm not a perfect man. I'm not a perfect president, but I promise you this -- and I've kept this promise -- I will always tell you what I believe and I will always tell you where I stand."

"If you stick with me, we're going to finish what we started in 2008," Obama said.

Later in the night, Obama told donors the nation was still dealing with a "difficult economy and that's why this is going to be a close race. I've got to tell you, if we weren't coming out of this extraordinary recession, I think the American people would make their decision very quickly," Obama said.

"But we've gone through three tough years. The other side has been able to sit on the sidelines and say `no' to everything, not cooperate and then simply try to point the finger and say, somehow this should have been fixed," the president said.

Before returning to Washington, the president made a short, impromptu visit to his red brick home in the city's Kenwood neighborhood, arriving around 9:45 p.m. local time. His motorcade waited along his block as the president checked out his old house.

Earlier, at a nearby fundraiser with neighbors, the president joked: "Is somebody mowing the grass in front of my house? I'm going to go over there and check. I don't want you guys talking about me."

Obama also checked in with his campaign, visiting his headquarters for the first time. The White House said Obama wanted to show his appreciation to his campaign staff with the surprise visit but the White House kept the moment private. Reporters traveling with the president were not allowed to witness the visit by Obama, who has insisted he is focused on governing, not campaigning.

A White House statement said Obama thanked his staffers for their hard work and encouraged them, saying that he hoped to run "a campaign that embodies the values we're fighting for."

Obama's campaign has hauled in more than $150 million through September, but Democrats say they will need to compete with Republican-leaning outside groups that can raise and spend unlimited amounts of money to back specific candidates.

Obama's event at the University of Illinois had ticket prices starting at $44 per person and he attended a pair of pricier fundraisers with tickets ranging from $7,500 for one event and $35,800 per couple for the other.

At the Lincoln Park home of Fred Eychaner, a Chicago media mogul, Obama joined with some financial backers who had supported him since he served in the Illinois state senate. The president said he had stayed true to the vision he had laid out as a local candidate long ago and his agenda as a presidential candidate four years ago.

"The reason I was successful was not because I was a flawless candidate or I ran a flawless campaign but it was because together we were able to give voice to this shared vision of what America should be. And I want you to know that I have kept faith with that vision all these years," Obama said to a dinner audience that included former Senate colleagues Dick Durbin of Illinois and Claire McCaskill of Missouri and Illinois Gov. Pat Quinn.

Obama's re-election campaign and the Democratic National Committee set a combined fundraising goal of $60 million for the final three months of 2011. The campaign is expected to release its fundraising report before the end of the month.

Romney's campaign said Wednesday it had collected $56 million for the primary through Dec. 31 and has more than $19 million in the bank, far outpacing his opponents' fundraising.

Obama told his Chicago supporters that "this will be my last campaign," joking that his one-time mentor, former White House counsel Abner Mikva, used to tell him that "'being friends with a politician is like permanently having a child in college.' Every year, it's another tuition check. But I'm finally graduating."