(Reuters) - Hispanics and Democratic lawmakers furious over Arizona's harsh crackdown on illegal immigrants expect huge weekend rallies across the United States, piling pressure on President Barack Obama to overhaul immigration laws in this election year. Protest organizers on Wednesday said outrage over the Arizona law -- which seeks to drive illegal immigrants out of the state bordering Mexico -- has galvanized Latinos and would translate into a higher turnout for May Day rallies in more than 70 U.S. cities.