U.S. Senator John McCain, pounded from the GOP right by conservatives on immigration and from moderates on his support for the president's Iraq policies, faces another challenge this week -- trying to scoop campaign cash from California's political ATM while being elbowed by a crowd of presidential hopefuls. The presidential candidates who have been crisscrossing the Golden State this week include the Republican front-runner, former New York Mayor Rudy Giuliani, who just concluded a fundraising trip; former Massachusetts Gov. Mitt Romney, who visits Southern California and San Francisco on Wednesday for fundraising; and a new and potentially formidable GOP challenger,...