LOS ANGELES - Democrats Barack Obama and Hillary Rodham Clinton sought common ground Thursday on basic Democratic policies on immigration, health care and tax relief in their first one-on-one debate, but grew testy at times in trying to distinguish themselves as the candidate best able to assume the presidency. Just days before the Super Tuesday contests, the two alternated addressing each other cordially with swipes, underscoring the high stakes of the upcoming contests. The debate came on the day when Obama's campaign reported raising a staggering $32 million in January, cash aplenty to advertise all through the Super Tuesday states,...