Senate Majority Leader Harry Reid is prepared to run a sharply negative campaign if that’s what it takes to win reelection next year, with a top adviser predicting that the Nevada Democrat will “vaporize” his Republican challengers with attack ads. Trailing in the polls and under constant attack from the GOP, Reid’s campaign has just launched a warm-and-fuzzy million-dollar ad campaign to reintroduce the veteran senator to his constituents. But Reid’s team also wants to be the one that introduces lesser-known opponents to the electorate — and will be ready, when the time comes, to unleash a torrent of ads...