There is strong evidence that November's Democratic sweep may be more than a one-shot reaction to an unpopular president and his war--it might be one of those pivotal elections leading to a lasting, long-term majority in the Congress and potentially the presidency. Democrats took control of Congress, making history by taking 30 House and six Senate seats without losing a single incumbent or open race. This was especially impressive against a House so gerrymandered that 95 percent of incumbents tend to keep their seats. In all, nearly 58 percent of the total national congressional vote went to the Democrats, as...