New York Times: As Democrats strained to win over crucial holdouts on the way to narrow, party-line approval of global warming legislation, they were dogged by a critical question: Has the political climate changed since 1993? Veteran members of both parties vividly remember when many House Democrats, in the early months of the Clinton administration, reluctantly backed a proposed B.T.U. tax – a new levy on each unit of energy consumed – only to see it ignored by the Senate and seized as a campaign …