Correction: An earlier version of this story misspelled the last name of Iowa Democratic Party Chairman Scott Brennan. This version has been corrected.

Campaign buttons are ready for distribution at an Iowa kickoff event for the national Ready for Hillary group led by Craig Smith, senior adviser to the Ready for Hillary group, in Des Moines on Jan. 25, 2014. (Justin Hayworth/AP)

In the annals of Iowa politics, there may be no precedent for what happened at a downtown brewery here this weekend: Two years out from the state’s next caucuses, Democrats of all stripes began building a presidential campaign without a candidate.

Hillary Rodham Clinton is not officially running for anything. But here in the first-in-the-nation caucus state that bedeviled her in 2008, Democrats are busy laying the groundwork for what they see as Clinton’s near-certain 2016 presidential campaign.

Over a marathon day of strategy sessions, the Democratic Party’s patchwork coalition was fully represented: labor leaders, elected officials, statewide and local candidates, liberal activists, women, gays, seniors and 20-somethings. State party chairman Scott Brennan was here, too, as were strategists and foot soldiers who helped President Obama’s 2008 Iowa triumph.

Ready for Hillary, an independent super PAC trying to organize grass-roots supporters behind Clinton, hosted five separate roundtable sessions Saturday that were attended by a total of well over 100 Democratic leaders and ­activists. The group recently organized in New Hampshire and is planning visits to South Carolina and Nevada — all early states on the presidential calendar.

“I’ve been organizing in the Iowa caucuses since 1979. I was for [Edward M.] Kennedy over [Jimmy] Carter,” said Teresa Vilmain, Clinton’s 2008 Iowa state director. “This early out, with the people in this room getting together — the serious Obama organizers and the serious Hillary organizers — that really never happens.”

The organizing effort demonstrated that, should Clinton run, it will be very difficult for Vice President Biden or another Democrat to mount a credible challenge. Priorities USA Action, the heavyweight liberal super PAC that led attacks against Republican Mitt Romney in 2012, has reoriented itself to fund a media campaign supporting Clinton.

The former secretary of state’s early advantages under­score the new legal landscape that allows independent groups to more easily raise unlimited money. In addition to assembling grass-roots coalitions in early voting states, Ready for Hillary is hosting fundraisers and grass-roots events from New York and San Francisco to less traveled locales such as Grand Rapids, Mich., and Youngstown, Ohio. The typical minimum donation is $20.16.

Since being launched a year ago by Adam Parkhomenko and Allida Black, Ready for Hillary has assembled an e-mail list of 1.8 million supporters and raised money from 40,000 of them. Mitch Stewart and Jeremy Bird, two celebrated field organizers from Obama’s campaigns, are among the veteran consultants aiding the group.

“This is starting much earlier than anyone did in 2008,” Stewart said. “Building a relationship within those constituencies takes time. One of the focuses that we have right now with Ready for Hillary is to start that relationship process so that if Secretary Clinton were to run, there would be an infrastructure out in these states that would support a national campaign.”

Ready for Hillary is planning to recruit volunteers at all 99 Iowa county Democratic conventions in March and will dispatch surrogates across the state for pro-Clinton events this spring. The group also is considering packing a bus with supporters and following Clinton on her nationwide book tour this summer.

The group’s challenge is to effectively channel enthusiasm for Clinton’s candidacy without doing anything to damage her politically. Still undetermined, of course, is whether Clinton — if she runs — will even compete in Iowa; in 2008, she considered skipping the state altogether.

Craig Smith, an operative from Bill Clinton’s 1992 campaign who served in his White House, is the Ready for Hillary senior adviser who convened the Iowa sessions. He told stories of elections he helped win for clients in Albania and Slovenia to demonstrate his experience in grass-roots organizing.

“I don’t know what she’s going to do, and I don’t know when she’s going to do it,” Smith said of Hillary Clinton.

The group is building a supporter database that could legally be transferred to Clinton’s campaign. (If she doesn’t run, Smith said, Ready for Hillary may transfer its data to the eventual Democratic nominee or to Priorities USA Action.)

“The doors are open,” Smith said. “It’s a clean slate. Everybody gets in. We want to send a message to her: If you get ready, we’ll be ready.”

These uncharted waters are leading to some confusion and doubts. State Sen. Janet Petersen (D), a key Obama supporter in 2008, asked Smith, “You want them to organize around a PAC or a candidate?”

Later, Vilmain said, “The problem is you create this monster — this opportunity for all these people to come here. The question is, what will they do before she decides? By the sheer force of nature, people will select themselves as leaders. There’s no boss except their energy.”

Ready for Hillary officials said they have had no contact with Clinton or her family. Asked about the Iowa efforts, Clinton spokesman Nick Merrill said, “They are an independent entity acting entirely on their own.”

Ready for Hillary opened all of Saturday’s strategy sessions to the news media — an unusual move, but one Parkhomenko said signals that supporters want Clinton to run an open and transparent campaign. What followed were frank but cordial assessments of the pratfalls that led to Clinton’s third-place finish in Iowa in 2008 and ideas about how to do better.

There was plenty of advice: Come early and come often. Slim down your entourage and ignore your consultants. Ditch the big rallies in favor of more intimate coffee shop visits. Be nimble and authentic. Listen, listen and listen some more. Embrace your potential to crack the proverbial glass ceiling, but make your campaign about much more than putting a woman in the White House. Most of all, don’t let anyone view your nomination as a coronation. You will have to earn it.

“Too many people thought it was preordained” that Clinton would be nominated in 2008, said Phyllis Peters, 55, of Ames, who knocked on doors for her that year. “You can’t skip the coffee shops and Red Hat clubs. You’ve got to do the retail politics. She tried, but it was a little sluggish. She needs to be more agile.”

State Sen. Jack Hatch, the leading Democratic candidate for governor in 2014 and a Clinton supporter, said, “They need a lightning-strike campaign — more spontaneous, less planning, show her roots as an organizer. Yes, it will be difficult. But our state won’t change how we approach caucuses based on the individual.”

Among Clinton’s backers here, there was some anxiety that she could lose, although nobody could explain how exactly that might happen.

“As Democrats, we always like a tiff, and there could be someone who comes out here next year and gets in,” said Jerry Crawford, a longtime Democratic leader here and Clinton’s 2008 Midwest co-chairman. “It’s our job to make sure that doesn’t happen.”

Greg Hauenstein, 29, who moved to Iowa in 2007 to work for Obama and hasn’t left, said of Clinton, “She needs to listen — listen. It has to be a bottom-up campaign. The inevitability argument goes over with Iowans about as well as a flat tire.”