The stock market staged a broad advance today, showing signs of life after the stalemate of the past several weeks. Analysts said there was no single development in the news to ``explain'' the rally. However, they said, it appeared some traders were bidding for stocks simply because the market hasn't sold off lately despite a long list of worries and uncertainties. Among those problems are the approaching first anniversary of Black Monday on Oct. 19, which is presumed to be casting a pall over the market. In addition, investors are said to be reluctant to commit themselves before they can get a clearer idea of where government economic policy is headed after the election of a new president. Nevertheless, brokers said money managers at some investing institutions seemed interested in adding stocks to their portfolios before they make reports to their clients for the third quarter, which ends with Friday's session. ``The market has been lifeless for so long. It started to move up, and gave traders a sense of direction,'' said Hugh Johnson at First Albany Corp. in Albany, N.Y. ``After that they jumped on board, with a little encouragement from the bond market.''