IN JUST two weeks, Fred Thompson will finally announce his formal entry into the 2008 presidential race and instantly become the biggest Republican threat to Rudy Giuliani. The long-anticipated move by the former "Law and Order" star begins today with his arrival at the Iowa State Fair, where he will face his first real test before actual voters. Giuliani still holds a 10-point advantage over him in national polls, according to RealClearPolitics, but Thompson has seen his own support steadily grow while Giuliani's slowly erodes, from a high of nearly 40 percent earlier this year to below 30 percent now....
