Alberto Cardenas, who escaped from communist Cuba when he was 12, won election Wednesday without opposition as the chairman of the American Conservative Union, the first new head of the prominent conservative organization in more than a quarter-century.

Mr. Cardenas, a prominent Miami attorney and a former chairman of the Florida Republican Party, also becomes the first Hispanic to lead a major national conservative organization.Alberto Cardenas, who escaped from communist Cuba when he was 12, won election Wednesday without opposition as the chairman of the American Conservative Union, the first new head of the prominent conservative organization in more than a quarter-century.

“I’m honored and humbled to be accorded this responsibility by an ACU board whose members, in many cases, were movement conservatives before I was and who dedicated their lives to the Founding Father’s principles of limited government, self-reliance and personal freedom,” Mr. Cardenas said.

With the vote of the 31-member ACU board, Mr. Cardenas, 63, succeeds David A. Keene, who has served as ACU chairman since 1984.

Mr. Keene, 65, informed the ACU board some time ago that he would be stepping down in advance of his expected election as president of the National Rifle Association in April.

However, Mr. Cardenas will not succeed Mr. Keene as head of ACU’s big-draw annual event, the Conservative Political Action Conference, until the three-day CPAC’s conclusion at the Marriott Wardman Park Hotel on Saturday.

With more than 11,000 activists from around the country expected to attend this week, according to Mr. Keene, CPAC is the largest and most prestigious gathering in the country of conservatives of all stripes.

In 1975, Mr. Keene tapped Mr. Cardenas, a pro-life Catholic, to be Florida co-chairman of Ronald Reagan’s first campaign for the GOP presidential nomination. Mr. Cardenas later won election as chairman of the state’s Republican Party. He is credited with helping lead the party’s resurgence in the state, which now boasts a Republican governor and a rising party star in freshman Sen. Marco Rubio.

Mr. Keene’s political career began as national chairman of Young Americans for Freedom. He served as a senior aide to former Vice President Spiro Agnew in the 1960s and as executive assistant to former New York Sen. James Buckley. He also served as an adviser to the presidential campaigns of Ronald Reagan, George H.W. Bush and Bob Dole.

Mr. Cardenas and Mr. Keene are longtime friends and political allies — both supported the 2008 GOP presidential nomination campaign of former Massachusetts Gov. Mitt Romney.

Former U.N. Ambassador John Bolton, in a letter to fellow ACU board members, called Mr. Cardenas “a committed conservative with a remarkable life story.”

Mr. Cardenas, some of whose relatives died at the hands of Cuba’s Castro regime, gained new prominence as part of a U.S. delegation attending the swearing-in of a Latin American president during the George W. Bush administration. Cuban President Fidel Castro was also in attendance, and when he arose to speak, Mr. Cardenas jumped to his feet and turned his back on the communist leader and held that posture during Mr. Castro’s entire speech.

Mr. Cardenas later confronted Mr. Castro directly, shouting “Asesino” — “Assassin” — at the Cuban strongman as he passed by. Mr. Castro’s security detail confronted Mr. Cardenas but was stopped short when he flashed his U.S. delegation credentials at them.

Mr. Cardenas was an employer of — and has been a friend and mentor to — Mr. Rubio, a fellow Cuban-American.

Mr. Cardenas and his wife of 32 years, Diane, have five children.