After the 1947 Polish legislative election, marked by electoral fraud, Bierut was made the first post-war President of Poland. In 1952, the new Constitution of the Polish People's Republic (until then known as the Republic of Poland) abolished the position of president and a Marxist–Leninist government was officially imposed. Bierut supported the radical Stalinist policies as well as the systematic introduction of socialist realism in Poland. His regime was marked by a silent terror – he presided over the hunting down of armed opposition members and their eventual murder at the hands of the Ministry of Public Security (UB), including some former members of the Home Army. Under Bierut's supervision, the UB evolved into a notorious secret police which was, according to some sources, responsible for the execution of tens of thousands of political opponents or suspects, six thousand according to the Hoover Institution. As Poland's "de facto" leader, he resided in the Belweder Palace and headed the Polish United Workers' Party from the party headquarters at New World Street in central Warsaw, known as "Dom Partii". He was also the chief proponent for the reconstruction of Warsaw (rebuilding of the historic district) and the erection of the Palace of Culture and Science.