SEVEN years after he disappeared into seeming political oblivion, Newt Gingrich, the former Republican revolutionary who became President Bill Clinton’s congressional arch nemesis, is plotting an eye-catching comeback.The author of the Republican party’s 1990s declaration of intent, Contract with America, now has a new political manifesto. He will begin selling it this week in those states that traditionally make or break the ambitions of politicians who want to be president. Gingrich will arrive in New Hampshire tomorrow and will travel to Iowa next month. His visits to the two states that vote first in the presidential primaries have ignited speculation...