How Cafta Passed House by 2 Votes
Cliffhanger House vote approving Central American Free Trade Agreement highlights messy compromises necessary to overcome deep antagonism in many quarters toward trade-opening agreements; Democrats charge Republicans with buying votes and forcing members to vote against their consciences; Republican Rep Robin Hayes of North Carolina says he was convinced to change his vote after Speaker Dennis Hastert pledged to push to help his district with jobs; Hayes vote was decisive to trade pact, which passed by two votes; Bush administration officials say ultimate goal is one of high principle: opening of United States to greater competition and engagement with poorer neighbors; says liberation from trade barriers would benefit Americans as well as their neighbors; photos (M)