The 2008 Spanish general election was held on Sunday, 9 March 2008, to elect the 9th Cortes Generales of the Kingdom of Spain. All 350 seats in the Congress of Deputies were up for election, as well as 208 of 264 seats in the Senate. After four years of growing bipolarisation of Spanish politics, the election saw a record result for both ruling Spanish Socialist Workers' Party (PSOE) and opposition People's Party (PP), together obtaining more than 83% of the vote share—over 21 million votes—and 92% of the Congress seats. The PSOE under José Luis Rodríguez Zapatero benefitted from tactical voting against the PP and emerged as the most-voted party just 7 seats short of an overall majority. On the other hand, Mariano Rajoy's PP saw an increase in its vote share and seat count but remained unable to overtake the Socialists. United Left (IU) had its worst general election performance ever with less than 4% and 2 seats. Regional nationalist parties Convergence and Union (CiU), Republican Left of Catalonia (ERC), Basque Nationalist Party (PNV) or Aragonese Union (CHA) were also hurt by the massive tactical voting towards the PSOE, falling to historical lows of popular support. Union, Progress and Democracy (UPyD), with 1 seat and slightly more than 300,000 votes, became the first nationwide party aside from PSOE, PP and IU entering in parliament in over two decades. Zapatero was sworn in as Prime Minister of Spain for a second term in office in April 2008, just as the Spanish economy began showing signs of fatigue and economic slowdown after a decade of growth. Overview Electoral system The Spanish Cortes Generales were envisaged as an imperfect bicameral system. The Congress of Deputies had greater legislative power than the Senate, having the ability to vote confidence in or withdraw it from a prime minister and to override Senate vetoes by an absolute majority of votes. Nonetheless, the Senate possessed a few exclusive (yet limited in number) functions—such as its role in constitutional amendment—which were not subject to the Congress' override. Voting for the Cortes Generales was on the basis of universal suffrage, which comprised all nationals over 18 years of age and in full enjoyment of their political rights. For the Congress of Deputies, 348 seats were elected using the D'Hondt method and a closed list proportional representation, with an electoral threshold of three percent of valid votes—which included blank