SAN LUIS, Arizona (Reuters) - When Michele Pena ran as a Republican candidate for the Arizona state legislature in a heavily Hispanic and Democratic-leaning district on the Mexican border, few believed she could win. Pena, the daughter of a Mexican immigrant, was a school volunteer and single mother with no political experience. She began with a campaign budget of just $1,600. She nonetheless scored an upset victory last year in the district, which is separated from Mexico by miles of border wall built under former President Donald Trump to keep out "bad hombres". "Hispanics go hard Democrat there all the...