Almost all the polls are now showing Thompson in second with McCain losing support and Romney mired in single digits.
WASHINGTON - Former New York Mayor Rudy Giuliani continues to lead the Republican field in the USA Today/Gallup Poll, but former Tennessee Sen. Fred Thompson, who hasn't yet formally entered the race, for the first time edges into second place over Arizona Sen. John McCain.
The results show a Republican race that could be roiled by Thompson, who is targeting conservatives unsatisfied with their choices in the field so far. He is costing Giuliani most: A third of Thompson's supporters say they would otherwise back the former New York mayor.
Among Democrats, New York Sen. Hillary Rodham Clinton has regained a double-digit lead over Illinois Sen. Barack Obama, two weeks after the survey found the Democratic presidential rivals essentially tied.
Thompson bump expected in July.