DES MOINES — For Republicans, the long road to the 2016 presidential election began in earnest Saturday in Iowa when a group of potential candidates competed for support among conservatives in the state that will hold the country’s first nominating contest.

As many as eight possible candidates are to take part in the Iowa Freedom Summit, a marathon day of back-to-back speeches organized by Iowa’s conservative Republican Steve King, a member of the U.S. House of Representatives.

“Do you believe that the next president of the United States is going to be speaking from this stage today?” King asked in an introductory speech. “As do I,” he agreed when the audience clapped.

Early speakers were Republicans who do not harbor 2016 ambitions. They criticized Democratic President Barack Obama, accusing him of bungling the fight against Islamic State and violating the Constitution by unilaterally easing U.S. immigration policy.

“The president is not above the Constitution,” Iowa Sen. Chuck Grassley said.

The key names to watch are a pair of governors, Chris Christie of New Jersey and Scott Walker of Wisconsin, who were speaking in the afternoon.

Christie is viewed skeptically by many conservatives. How he crafts his message here could be critical. Many Republicans see Walker as a person to watch in spite of the early attention on the potential candidacies of Mitt Romney, the 2012 nominee, and former Florida Gov. Jeb Bush.

There are a variety of other people who will be at the event and who could emerge as major 2016 players, such as former Texas Gov. Rick Perry, who ran for the nomination and lost in 2012, and former Arkansas Gov. Mike Huckabee, who won Iowa in 2008 but lost the nomination.

Texas Sen. Ted Cruz also will speak along with former Hewlett-Packard Co. CEO Carly Fiorina, physician Ben Carson and former Pennsylvania Sen. Rick Santorum.

Steering clear of the event were Bush, Romney, Florida Sen. Marco Rubio and Kentucky Sen. Rand Paul.

Iowa holds the first nominating contest of 2016 when Republicans and Democrats gather early next year for caucuses. Republicans here have not picked the eventual nominee since they went for George W. Bush in 2004. But the caucuses do serve a valuable role in winnowing the field.

“This will serve as sort of the unofficial kickoff to the Iowa caucus season for 2016,” Tim Albrecht, an Iowa Republican strategist, said. “It’s a great first look at how potential candidates stack up against each other.”

On Sunday, Cruz will join Rubio and Paul in Palm Springs, California, where about 450 people are attending a winter “seminar” organized by a network of groups founded by brothers Charles and David Koch.