"Excruciating" is how Clinton, in her memoir "Hard Choices," described her third-place finish in the caucuses. She didn't set foot on Iowa soil for more than six years.
Now, after Clinton's Sunday announcement of a second presidential campaign, she will again head for Iowa, which holds the first presidential nominating contest in the nation.
Interviews with voters and Democratic operatives here say the critical test this time will be whether Clinton — once again viewed as the inevitable Democratic nominee — learned from last time. Can she connect with Iowans as a warm, Midwestern-nice neighbor, the opposite of her 2008 image as distant and presumptive?
"She needs to get out of coronation mode and go out and meet people and really listen to everybody and see what they have to say," said Cameron Wright, a 22-year-old law student who supports Clinton's candidacy.
That, in fact, is what Clinton's campaign-team-in-waiting has telegraphed as her strategy for 2016: the opposite, mostly, of how she began her last campaign, with rock-star-like rallies.
At this point, Clinton does not appear to be facing an opponent as formidable as then-Illinois Sen.
In a state where voters are used to meeting candidates and peppering them with questions, Clinton's 2008 disdain for that sort of ring-kissing rubbed many Iowans the wrong way.
"It wasn't a grass-roots campaign," said Virginia Peterson, a 76-year-old retiree from Johnston who is now supporting Clinton. "I waited a long time to make up my mind [and] when I decided to support Obama, I had not received a call from the Hillary group and so I never attended any of Clinton's functions. That's really important. We are used to getting invited to small groups."
Carrie Giddens, who served as the Iowa Democratic Party spokeswoman during the 2008 cycle and now teaches political writing at American University, said the fault then centered on Clinton's national apparatus ignoring the counsel of its Iowa advisors.
"She needs to trust the people in Iowa who she's chosen to run her campaign because they know Iowa," Giddens said. "That was not the case last time. I think what happened last time is the national campaign thought they more knew what they were doing and didn't understand what was going on on the ground. The people she's selected now know what they're doing. If they are allowed to do what they do, she will have better results."
Giddens noted that the potential Democratic challengers are significantly weaker than seven years ago. Clinton holds a 40-point lead over the second-ranking Democrat in the closest major poll of Hawkeye voters.
Yet there has been some slippage in Clinton's standing as she nears an official announcement. A recent Quinnipiac poll of Iowa voters showed them split over whether Clinton was trustworthy, and more than a third said they were less likely to vote for her given the recent controversy over her use of a private email server as secretary of State.
Jennifer Lunsford, a member of the state party's central committee, said Clinton would have to address those concerns. Lunsford has not made up her mind but says Clinton is her top choice now.
"As long as she answers the questions the best she can and is honest about it, people will let it go," said the 36-year-old, who works in telecommunications.
Lunsford was among several voters who said they would like to see a contested primary, both to strengthen Clinton and to force her to take stands on issues that are popular among the party's liberal faction — such as income inequality.
"I don't know that I would support another candidate, but I want there to be some debate," Peterson said. "I do think it would make her a better candidate in the general election. I think it would make her a better president."
Nick Cerrato, 48, said that while he supported the notion of electing the first female president, he was looking for "the best horse in the race."
"We might need more horses," said Cerrato, an official with a local plumbers union.
Two Democrats who are considering a run for president — former Maryland Gov. Martin O’Malley and former Virginia Sen.
In the front entryway, supporters of popular liberal Sen.
"We believe Sen. Warren deserves to be on the ticket," said Taylor Stout, a 24-year-old volunteer for a national effort to draft Warren to run. "She's out fighting for middle-class Americans, going up against Wall Street, wanting to reform students' loans — really all the hot topics that are going to come up in the next election."
Both O'Malley and Webb hit Warrenesque notes. O'Malley highlighted his record, such as increasing the minimum wage in Maryland. Without mentioning Clinton by name, Webb obliquely criticized her tenure as secretary of State as well as her support for the Iraq war as a senator.
Both men face nearly overwhelming hurdles if they decide to run. But Obama's experience in the state in 2008 boosts the hopes of every underdog.
"Even though Hillary Clinton is very strong, if there are other candidates in Iowa and New Hampshire, because they're small, they can come and do a lot being on the ground," said Jodi Tomlonovic, 60, of Des Moines, who supports Clinton. "For Iowa, she does need to be here and really articulate her message. She wasn't here very much last time and President Obama did a very good job."