WARSAW (Reuters) - Donald Tusk will be the first Polish prime minister since the fall of communism more than two decades ago to rule for a second consecutive term after his centre-right Civic Platform trounced rivals in an election, cheering the markets. With 64 percent of the votes counted, Tusk's pro-business party had won 37.5 percent of votes in Sunday's election, short of an absolute majority but far ahead of Jaroslaw Kaczynski's nationalist-conservative Law and Justice party on 30.6 percent. Financial markets will welcome Tusk's victory, which points to four more years of relative political and economic stability.