nation. The Union of Christian and Centre Democrats asked for a proportional electoral law that would not damage small parties, and was generally more willing to discuss compromises with the moderate wing of the opposition. Difficulties in negotiating an agreement caused some internal unrest in the Berlusconi government in 2003, but they were mostly overcome and the law including devolution of powers to the regions, Federal Senate, and strong premiership, was passed by the Senate in April 2004; it was slightly modified by the Chamber of Deputies in October 2004, and again in October 2005, and finally approved by the Senate on 16 November 2005, with a narrow majority. Approval in a referendum is necessary to amend the Italian constitution without a qualified two-thirds parliamentary majority. The referendum was held on 25–26 July 2006 and resulted in the rejection of the constitutional reform, with 61.3% of voters casting ballots against it. 2006 general election and opposition Operating under a new electoral law written unilaterally by the governing parties with strong criticism from the parliamentary opposition, the April 2006 general election was held. The results of this election handed Romano Prodi's centre-left coalition, known as The Union (Berlusconi's opposition), a very thin majority: 49.8% against 49.7% for the centre-right coalition House of Freedoms in the Lower House, and a two-senator lead in the Senate (158 senators for The Union and 156 for the House of Freedoms). The Court of Cassation subsequently validated the voting procedures and determined that the election process was constitutional. According to the new electoral rules, The Union, nicknamed "The Soviet Union" by Berlusconi, with a margin of only 25,224 votes (out of over 38 million voters) won 348 seats (compared to 281 for the House of Freedoms) in the lower house given to whichever coalition of parties was awarded more votes as a result of the majority bonus system. This electoral law, approved shortly before the election by Berlusconi's coalition in an attempt to improve their chances of winning the election, led to the coalition's defeat and gave Prodi the chance to form a new cabinet. Prodi's coalition government consisted of a large number of smaller parties. If only one of these nine parties that formed The Union withdrew its support to Prodi, his government would have collapsed. This situation was also the result of the new electoral system. Centrist parties such as the Union of Christian