Democrats face an uphill battle to recapture control of the House in November's midterm elections, while Republicans have marginally improved their position in what remains a tense and wide-open fight for control of the Senate, according to party strategists, independent analysts and current polls. September has seen Republican prospects brighten, particularly in New Jersey, where ethics problems have called into question what once seemed solid reelection prospects for Sen. Robert G. Torricelli, the most vulnerable Democrat in the nation. Republicans also have increased their chances of retaining the Senate seat in New Hampshire. And because of a controversy over a...