"... they could force otherwise safe Democratic incumbents like Minority Leader Tom Daschle (S.D.) and Minority Whip Harry Reid (Nevada) to invest heavily to defend their seats."
Harry Reid won his last election by fewer than 500 votes ... as an incumbent. The demographics of Nevada are changing away from his labor/econazi base. Reid is on the hot seat and if the Republicans field a half-way decent candidate, "Senator Stonewall" is toast.
P.S. Daschle is so safe either.