By Ray Fleming IT is a curiosity of the American constitution that Congressional elections held in early November do not take effect until the following January. Hence the expression lame duck for the Congressional sessions taking place in Washington at the moment -- in the House of Representatives, especially, there are several lawmakers defeated in the recent mid-term election still sitting in their old seats, taking part in the debates and voting. Sometimes this does not matter greatly but this year it is seriously affecting the progress that President Obama can make with legislation introduced in Congress before the November elections, of which the most important is the new nuclear arms reduction treaty negotiated with Russia many months ago but still needing US Congressional approval. This treaty provides for a one-third reduction of the long-range nuclear arsenals held by Russia and the United States; apart from its intrinsic importance it is also a vital stepping stone towards President Obama's vision of a world free of all nuclear weapons. Whether or not the President can get approval of this treaty before a Congress more hostile to his policies assembles in January is an open question. The behaviour of lame duck Congresses is always difficult to predict, partly because of the presence of already voted-out members and partly because of concern about the priorities of those arriving in January.