Yet again, Hillary Rodham Clinton has shown that she can be well ahead of her close rivals. This time, she’s the top choice when people werre asked which major 2008 presidential candidate would make the scariest Halloween costume.Thirty-seven percent in an Associated Press-Ipsos survey this month chose Clinton. Fourteen percent selected former New York Mayor Rudy Giuliani, who is expected to lead Republicans in national polls. Surprisingly, no other candidate was found to exceed 6 percent. The New York senator was the choice of four in 10 men and one-third of women. While a predictable two-thirds of Republicans picked her, she also was the choice of 18 percent of Democrats. Nearly one-third of independents, nearly half of whites and just over half of conservatives and white evangelicals selected her. Rudy Giuliani was the choice of 17 percent of men and 12 percent of women. About one-fifth of minorities and one-quarter of Democrats also picked him as their rightful choice.