Spaniards angry with 21 percent unemployment and seemingly endless corruption cases are voting in an historic national election — and the country's traditional two-party political system may be broken up in this vote by strong showings for two new upstart parties.

Spain has been dominated for more than three decades by the ruling Popular Party and the main opposition Socialists, which have alternated running the government.

But many voters casting ballots on Sunday were expected to support the business-friendly Ciudadanos party or the far-left Podemos party.

Polls predict the right-of-center Popular Party will get the most votes but not enough to retain its parliamentary majority.

Prime Minister Mariano Rajoy has said he would seek an alliance with politicians outside his Popular Party to prevent a leftist coalition from taking power.