U.S. Rep. Raúl Grijalva easily overcame the first primary-election challengers he's faced since he was elected to Congress in 2002.

He'll face Republican Gabriela Saucedo Mercer in the general election race to represent a district that includes the western part of the Tucson area, Santa Cruz County, part of Maricopa County and Southwestern Arizona.

Grijalva ran unopposed in the past four primary elections, but this year he faced two challengers: Yuma businesswoman and former state lawmaker Amanda Aguirre and Tucson physician Manny Arreguin.

They fell far short of Grijalva in the Democratic primary Tuesday night. With more than half the precincts reporting, Grijalva had 66 percent of the vote, to Aguirre's 25 percent and Arreguin's 9 percent.

In their campaigns, both challengers emphasized Grijalva's 2010 comments encouraging a boycott of Arizona as a response to the passage of state immigration law SB 1070, and they pointed out the public's low approval ratings of Congress.

"We kind of figured with the way the district was set up that challengers would come in the primary to weaken us so we could be more vulnerable in the general," Grijalva said.

The newly formed district, he said, will benefit him because there are more working-class voters, more supporters of President Obama "and a very threatened middle class."

Saucedo Mercer had 63 percent of the vote to beat fellow Republican Jaime Vasquez, who had 36 percent. At the Republican get-together at El Parador Restaurant, Saucedo Mercer said she won because voters "want change, real change."

Saucedo Mercer, who is an immigrant from Mexico, said she plans to reach out to Latino voters in the general election. "I'll continue reaching out to voters, especially the ones who have been disenfranchised with him, and then plead my case," she said.

A Libertarian candidate, Blanca Guerra will also face Grijalva and Saucedo Mercer in the November general election.

Star reporters Jamar Younger, Kim Smith and Joseph Treviño contributed to this report. Contact reporter Tim Steller at tsteller@azstarnet.com or 807-8427.