Democratic strategists, seeing this election as the best opportunity for the party since the 1974 post-Watergate blowout, are urging party leaders to go for broke. James Carville called it a “twicein-a-lifetime environment” that could give Democrats “gains large enough to affect congressional control over this decade.” The Democratic National Committee has already said it is taking out a loan of up to $10 million to plow into hot Senate races in Tennessee, Virginia and New Jersey. And the Democratic Congressional Campaign Committee wrote checks for at least $12 million last week, primarily for ad buys targeting 30 at-risk Republican districts...