The most wide-open Republican presidential nomination campaign in memory had its unofficial opening here on Saturday at a gathering that highlighted anew the thorny path ahead for candidates as they try to attract support from the party’s conservative base without compromising their hopes of winning a general election.

In the coming months, the large field of candidates will feel a strong gravitational pull to the right by activists in a party that has become more conservative over the past eight years. That the first major conclave of prospective candidates came here at an event hosted by Rep. Steve King (R-Iowa), one of the party’s most outspoken voices on immigration and other issues, only served to underscore the potential risks ahead.

The lessons of Mitt Romney’s ultimately unsuccessful campaign of 2012 are still fresh in the minds of candidates and strategists. In an effort to demonstrate his bona fides to the right — at one point he described himself as “severely conservative” — Romney took positions on immigration and taxes that dogged him throughout the fall 2012 campaign.

Avoiding those kinds of mistakes will be at the top of nearly every candidate’s handbook for running. But with a field of candidates that could approach a dozen or more, and with competition fierce to find at least a slice of the party electorate upon which to build a campaign foundation, there will be an inevitable tendency to push too far, with potentially costly consequences.

“You have to know who you are, know why you’re running, know how to present your message and then not waver,” said Tim Pawlenty, the former Minnesota governor who ran unsuccessfully for the GOP nomination in 2012.

Rep. Steve King (R-Iowa), one of the party’s most outspoken voices on immigration and other issues, is hosting the Iowa Freedom Summit. (Charlie Neibergall/AP)

This year’s Republican presidential campaign is unique, not only in how wide open the race is but also because of the wealth of choices for voters from the party’s different wings or factions. Establishment Republicans, who long have been dominant in the nomination process, may be able to pick from Romney, former Florida governor Jeb Bush and New Jersey Gov. Chris Christie.

The most conservative party activists, who believe it is time for the GOP to nominate someone who is a true believer, could have even more choices. That group includes the two most recent winners of the Iowa caucuses — former Pennsylvania senator Rick Santorum and former Arkansas governor Mike Huckabee — as well as Sen. Ted Cruz of Texas, Louisiana Gov. Bobby Jindal and doctor Ben Carson.

Add in four others who could fit somewhere in between — Sen. Rand Paul of Kentucky, Sen. Marco Rubio of Florida, former Texas governor Rick Perry and Wisconsin Gov. Scott Walker — plus other dark-horse candidates struggling to gain some attention and the jockeying is likely to become ferocious, raising the stakes on finding ways to stand out in the crowd.

“The temptation will be to scratch the ideological itch of those in the room,” Matt Strawn, a former Iowa Republican Party chairman, said of events like the one here Saturday. “I would submit that those itches are best scratched in private, one-on-one conversations.”

The Iowa Freedom Summit, co-sponsored by Citizens United, drew nearly two dozen speakers — more than half a dozen of them now thinking seriously about running for the nomination — and a huge throng from the media, with an estimated 200 requesting credentials. Missing, however, were Bush, Romney, Rubio, Paul and Jindal.

More than 1,000 people packed an auditorium for a marathon day of speeches that offered the activists an early look at the presidential field, and one theme offered again and again was the importance of finding a true conservative to lead the party in 2016.

Speakers focused more of their attacks on Obama than on the Democrats’ leading expected 2016 candidate, Hillary Rodham Clinton. The sharpest attack on Clinton came from Carly Fiorina, who took note of the former secretary of state’s travels and said, “Flying is an action, not an accomplishment.”

There was a heavy emphasis on foreign policy throughout the day, and a similarity in the comments. Evident was a growing concern in GOP ranks about Obama’s response to recent terrorist attacks in Europe and unrest in the Middle East. Domestic policy featured prominently, but with the GOP in control of Congress and Obama managing foreign policy, ire was turned toward the White House.

Among the prospective presidential candidates, Cruz and Walker drew rousing ovations. An animated Walker called for “big and bold” conservative policies: “If you’re not afraid to go big and bold, you can actually get results.” Cruz, who has excited many conservative audiences, challenged others to demonstrate their conservative credentials by pointing to when they have stood and fought for them. “Talk is cheap,” he said.

Santorum said Republicans should focus policies on working people more than on business owners and entrepreneurs. Christie sought to win the conservative audience by stressing his opposition to abortion and his success in heavily Democratic New Jersey. When pro-immigration hecklers interrupted Christie, he playfully asked, “Don’t they know I am from New Jersey?” But neither got the kind of response that Walker and Cruz did.

There were few direct criticisms of one or another of the candidates, but businessman Donald Trump drew a wave of applause when he urged Republicans to avoid both Bush and Romney. “It can’t be Mitt, because Mitt ran and failed,” Trump said. Turning to Jeb Bush, he said the son and brother of presidents is “the last thing we need.” While Trump was flamboyant, Carson delivered his conservative message in a quiet, low-key style.

Though the Iowa caucuses are a year and some days away, it felt like caucus weekend in Des Moines. The lobby of the Marriott Hotel pulsed with activity late Friday night, particularly when former Alaska governor Sarah Palin arrived and soon fell into conversation with King and then briefly with former House speaker Newt Gingrich and his wife Callista, all surrounded by people snapping photos with their phones. Also in the lobby at the time was Santorum, who plans to spend five days in the state this week.

Though no one has formally announced a campaign, many of the candidates are actively moving toward it by establishing political action committees that can defray the costs of preparation and hiring staffs for their headquarters operation and to oversee organizing in some of the early states. And they are courting donors intensively.

As the speakers were testing their messages in Iowa, some candidates were heading for California for a weekend retreat hosted by billionaires Charles and David Koch, two of the most influential donors in the party.

King’s event came at the end of a week in which the new Republican majority in Congress began to flex its political muscles, dismissing President Obama’s State of the Union address as either misguided on domestic policy or naive on foreign policy.

But a party determined to show that it could govern responsibly also put on a messy display over legislation to restrict abortions, with House leaders having to pull one measure after some female members objected to it before later passing another bill that called for new federal restrictions. The White House said it would veto the measure.

Democrats were swift to say that what happened in the House showed that the Republican Party remains captive of its most extreme elements, and they were only too happy to hold up King and his summit in Des Moines as a further indication that the nomination process could soon be taken over by that wing of the party.

Just as the first of the speakers was preparing to take the stage in Des Moines, Brad Woodhouse of the progressive advocacy group American Bridge chastised the Republicans for coming to Iowa and “kissing Steve King’s ring.”

King brushed aside such criticism. “I’ve been called names for a long time, well before I was ever elected to the United States Congress,” he told reporters before leaving for Iowa. “I learned long ago that when they start calling you names, they’re only trying to marginalize you because they’ve lost the debate.”

Cruz offered this defense of King and his role in the party. “Most of the people in the media are not attempting to represent the American people and strongly disagree with the conservative values that Steve King represents and are shared across America,” he said in an interview.

Iowa Gov. Terry Branstad, in a telephone interview Friday morning, sought to play down the importance of Saturday’s forum, saying it was just “one of many events you’re going to see” in Iowa over the next year. He quickly pointed to an upcoming March agriculture summit in the state to which candidates from both parties have been invited.

Steve Schmidt, who was John McCain’s campaign chief in 2008, said running for the nomination is a character test of the candidates — a proving ground for delivering a message without being overly swayed by any particular audience or segment of the party.

Pointing to Saturday’s session in Iowa, he said: “These are events where you show your mettle. . . . The American people don’t evaluate candidates on an issue score card as much as they do on a strength and leadership basis.”

Iowa can be an especially difficult landscape for candidates, both because of the sizable influence of religious conservatives and because of such issues as ethanol subsidies, a policy that has been controversial for years but which most presidential candidates routinely have endorsed.

The demands on candidates who come to Iowa can be almost never-ending, and candidates find it difficult to resist the urge to try to meet as many of those demands as possible. “Iowa is littered with shiny objects that are very tempting for presidential candidates,” said GOP strategist Phil Musser, who was part of the Pawlenty team in 2012. “A successful candidate has to have patience and understand you don’t need to chase every one.”

Pawlenty, in a telephone interview Saturday, joked about the way he handled such demands. “We approached them incorrectly and unwisely,” he said. “And that is probably why people who run the second time run better than the first time.”

As tempting as it may be to skip events like the one in Iowa on Saturday, there is a risk involved. One risk is developing a reputation for dissing important elements of the Republican Party or of not being sufficiently in sync ideologically with the base, both potentially fatal politically.

“If you don’t go into those events and define yourself, you will be defined by your absence,” said Jeff Boeyink, the former chief of staff to Branstad and a Christie supporter for 2016. “One thing I admire about Christie, he’s not afraid to go anywhere.”

Candidates have their own concerns about this. John Brabender, top adviser to Santorum, noted that the former senator believes that in 2012, “he oftentimes allowed himself to be defined by what the questioners wanted to talk about rather than what he wanted to talk about.”

Group events can take on their own dynamic, making it difficult at times for candidates to resist running to the right with everyone else. At the same time, candidates must remember they are always speaking to multiple audiences at the same time — those in the hall and those who might be watching around the country — and to avoid what Brabender called a bidding war “to show they’re even more extreme on some issue than the person who spoke before them.”

Schmidt pointed to past examples when, in his view, candidates passed up opportunities to show their character. At a debate in Iowa in summer 2011, the candidates were asked whether they would accept a budget deal that included $10 in spending cuts for every $1 in new taxes. Nobody on the stage was willing to say yes.

At a Florida debate that year, some members of the audience booed a gay soldier who asked the candidates about the repeal of the military’s “Don’t Ask, Don’t Tell” policy. No candidate admonished those booing.

Immigration remains a potentially perilous issue for Republicans because of the importance of the Hispanic vote in the general election. King’s harsh anti-immigration rhetoric captures the conundrum for the candidates. “Whoever emerges as our nominee is going to have to confront the immigration issue,” Rep. Charlie Dent (R-Pa.) said in an interview. “It isn’t going away.”

Sen. Orrin G. Hatch (R-Utah), who ran for the GOP presidential nomination in 2000, pointed to Iowa’s conservative leanings among caucus attendees, describing the caucus process as “a difficult place for a moderate.”

Hatch said that after the rise of the tea party a few years ago, which pushed the party to the right, “we’ve seen that movement kind of taper off a bit.” He added, “I think the party is now more moderate conservative.”

That assertion will be put to the test, starting in Iowa this month and intensifying as the nomination contest ramps up over the course of the year.