It hasn't been easy. But the senator from New York appears to be growing on Iowa, home to the first-in-the-nation presidential caucuses.
A poll published yesterday by the Des Moines Register gave her 29 percent of the vote and a six-point lead - as big as she's had in any Iowa survey - in a tight three-way race with John Edwards and Barack Obama. Another poll has her slightly behind Obama.
No matter the numbers, Iowa remains a much tougher sell for Clinton than most of the other key, early states. That explains why this year, more than ever, the caucuses are the main event on the Democratic side.
In the national polls, Clinton is comfortably ahead in the contest for her party's nomination, looking stronger and better-financed than ever. In general election match-ups, she beats all comers.
In Iowa, though, she's getting a real battle from rivals who understand that a win for Clinton here would make her all but unstoppable, given her strength in the states that follow.
Talk to local Democrats, and you hear some express worries about her divisiveness and doubts about her electability.
"I like Hillary; I think she'd be a great president," said Larry Popenhagen, 55, a longtime county official in northeast Iowa who's trying to decide between Edwards and Obama. "But I don't want a nominee whom half the population already detests. Lifelong Republicans tell me they might vote Democrat this time. Not one of them, though, will vote for Hillary."
The competitiveness of the race is attributable in Iowa to a number of factors, the main one being that the race is far more fully engaged here than anywhere else.
Edwards has mounted a huge personal and organizational effort, Bill Richardson a significant media and on-the-ground campaign, Obama all of the above. Joe Biden practically lives here full time.
In addition, Clinton's opposition to the administration's policy in Iraq - she wants to end the war "as carefully and responsibly as we can" - isn't strong enough for some in a state that has always had an antiwar strain. Her Senate vote to authorize the war in 2002, which Obama has been stressing, has not been forgotten.
"I don't like the way she's handled the war vote, refusing to apologize for it," said Greg Holt, 45, a youth minister from Cedar Falls, who plans to choose between Obama and Richardson. "We have a president now who won't apologize for anything."
Clinton is also taking some heat over her support for a recent Senate amendment labeling Iran's Revolutionary Guard a "terrorist organization," seen in some quarters (but not by her) as a step toward U.S. military action.
Then, too, there is the sense in some quarters that she is too much the establishment candidate and the fact that the Clintons have never before run an Iowa caucus campaign; in 1992, when Bill Clinton got elected, Iowa had a favorite son candidate in Sen. Tom Harkin.
Finally, the senator from New York simply hasn't invested as much time in Iowa as the others, and local activists keep track of such things.
Through Sept. 30, she'd spent 31 days in the state as a candidate, which sounds like a lot except when compared with everyone else. Edwards had put in 66 days, Biden 64, Chris Dodd 45, Obama 44 and Richardson 40.
She has 21 offices in Iowa. But Obama has 27.
Beyond the question of quantity, there's the matter of quality.
"Her trips have all of the personal touch of a visit by Citicorp," said former state party chairman Dave Nagle, who's not supporting any candidate. "No one in Iowa goes to bed at night thinking Hillary's depending on me."
To whatever degree that's true, Clinton is trying to fix it. Yesterday at noontime, she spent an hour with a standing-room-only crowd of 500 in the tiny town of New Hampton, half of it answering questions.
"Please take a hard look at my campaign," she asked at the end. "Judge me for who I really am, not what others say about me. I can't do it without your help."
She had eight more stops planned, in towns big and small, before departing tomorrow.
"She's gaining momentum every day, every day, yes she is," said Linda Olson, 55, a punch-press operator from the town of Marengo. "She's got the most experience, the personal and political strength to be a leader. She's been in the White House; she knows how it works."
"If I had to decide today, I'd caucus for Edwards," said Dave Parsons, 54, a businessman from Iowa City. "But for some reason, with every week that goes by, Hillary seems less like a dragon lady to me."
As the intense campaigning continues, Edwards, who's on track to be the first candidate to visit all 99 counties, is trying to fend off doubts about his long-term prospects. Members of the Obama camp, pleased with their candidate's own four-day Iowa excursion last week, are hoping to pick up anyone who might abandon Edwards.
A lot of rank-and-file Iowa Democrats, whose enthusiasm for this race is extraordinary, are simply looking for a winner. They won't decide who that is until they have to, about three months from now.
"Change is not a strong enough word for what I want," said Linda Sturdevant, 62, a disabled dental hygienist from Washington, Iowa. "The Constitution has been trampled on - at no price to the people doing the trampling. The Democrats have to win."
Contact senior writer Larry Eichel at 215-854-2415 or firstname.lastname@example.org.