Mr. King, in an interview in his House office on Wednesday, was quick to point out that “I never talk about race, that for me it’s always about the Constitution and the rule of law.”

Doug Gross, a Republican strategist in Iowa, said there were dangers in Mr. Christie’s appearing to align himself with Mr. King. “Christie has to be careful,” Mr. Gross said. “If he attempts to pander, as Romney apparently did on immigration, he hurts himself.” (In a 2012 primary debate, Mr. Romney advocated “self-deportation” for millions of unauthorized immigrants.)

Mr. Christie’s advisers said he was attending both to contrast his views with Mr. King’s and to introduce himself to the conservative base.

“He may not tell everybody everything they want to hear, but there won’t be any question on where he stands on issues that are important to that group,” said Jeff Boeyink, an adviser to Mr. Christie in Iowa. “A candidate who comes from the perspective that Governor Christie comes from needs to engage in some of these environments if he’s going to be a full-spectrum candidate.”

Mr. King said his friendship with Mr. Christie dated to 2009, when Mr. Christie was questioned by the House Judiciary Committee, then controlled by Democrats, about no-bid contracts he had awarded as the United States attorney for New Jersey. Mr. King vigorously defended him. “Chris Christie remembered that,” Mr. King said.

The event on Saturday offers a golden opportunity for potential candidates to woo grass-roots activists, coming as the 2016 contenders are just beginning to build campaign infrastructures in early primary states.

A crowd of roughly 1,250 from around Iowa will be in the audience, and potential presidential candidates are appearing on a bill that surrounds them with heroes of the grass-roots right. Also scheduled to give speeches are Sarah Palin; Donald Trump; Newt Gingrich; Jim DeMint, the president of the conservative Heritage Foundation and a former senator from South Carolina; and Senator Joni Ernst of Iowa, who gave the Republican response to the president’s State of the Union address on Tuesday.