For the first time, Arizona has more independent than Democratic or Republican voters, a sign that residents are moving away from the hyperpartisan brand of politics that came to define the state in recent years. Also the state, pegged as intolerant after passing one of the nation’s most restrictive laws against illegal immigration in 2010, is projected to become majority Latino by 2030.

The shift injects a complicating element to a decidedly open Republican primary. Some campaigns have been struggling to strike the right tone: conservative enough to entice the party’s reliable base of conservative voters, but not too conservative to alienate the more moderate independents. Voters in the latter group could easily have the power to decide the election for governor, unless apathy, frustration or other factors keep them from the polls.

Their share of the electorate climbed to 35 percent from 25 percent in 2004, mirroring a national trend that reflected negative perceptions of Congress, the major political parties and government in general among American voters, according to an analysis by Gallup of the results of several polls that it carried out last year. But independents have invariably logged the lowest turnout rates among voting blocs in Arizona — 41 percent in the general election in 2010. (The turnout was 68 percent among Republicans and 56 percent among Democrats.)

“It’s very hard to motivate independents, because they don’t have this ideological zeal that motivates the right-wing extremists,” Bruce Merrill, a senior research fellow at the Morrison Institute for Public Policy at Arizona State University, said in an interview.