Allende won the 1970 Chilean presidential election as leader of the Unidad Popular ("Popular Unity") coalition. On 4 September 1970, he obtained a narrow plurality of 36.2% to 34.9% over Jorge Alessandri, a former president, with 27.8% going to a third candidate (Radomiro Tomic) of the Christian Democratic Party (PDC). According to the Chilean Constitution of the time, if no presidential candidate obtained a majority of the popular vote, Congress would choose one of the two candidates with the highest number of votes as the winner. Tradition was for Congress to vote for the candidate with the highest popular vote, regardless of margin. Indeed, former president Jorge Alessandri had been elected in 1958 with only 31.6% of the popular vote, defeating Allende.