If the New Hampshire race is like others in some respects, it is unique in at least one. Brown, 55, moved to the state to run. The race is his third for the Senate in five years. Shaheen, 67, is a known political commodity in New Hampshire. She was elected, to this Senate seat, in 2008 when Obama won the state. "She's won in a wave and lost in a wave," says former Rep. Frank Guinta, a Republican. "I think she's as susceptible as anyone is." That view — that even a well-established politician can lose if enough voters sour...