Before Spain's general elections Sunday, an official arranges a ballot box at a polling station in Madrid, Dec. 18, 2015. Reuters/Sergio Perez

Spaniards are set to take to the polls Sunday to vote in the country's general elections. Voters are set elect all 350 members of the Congress of Deputies, its lower house, and 208 of 266 members of the Senate, its upper house.

Amid the surging of two outsider parties, the elections are expected to be unlike any in recent memory. Since a transition to democracy in the 1970s the lion's share of Spanish elections have been dominated by the Spanish Socialist Workers' Party (PSOE) and the center-right People's Party (PP). Led by Prime Minister Mariano Rajoy, who is seeking re-election, the PP is currently in power. But the country was hit with a crippling recession through 2013, with the unemployment rate peaking at about 27 percent overall and at more than 50 percent among the younger generation, as the Guardian reported. The economic recovery has been slow, with the unemployment rate remaining above 20 percent.

Because of Spain's economic struggles, the anti-austerity party Podemos has shot up in the polls into double figures, percentagewise, despite its being founded in 2014: The party now holds more than 100 seats in regional legislatures. Another party, Ciudadanos, also has rapidly grown in popularity.

Members are elected to the congress through 50 multimember districts employing a proportional-representation system, with each district being home to a minimum of two members. Due to the rise of the two outsider parties, the results of the election are not easy to predict. The sole "certainty is that no party will get a majority in the 350-seat Congress," Politico's European edition contended. The elections Sunday could signal the beginning of a long road toward a potential coalition.

You can employ numerous methods to monitor election results. The Guardian will run a live blog with other extended coverage, which you can find here, and the outlet recommended tracking its Spain correspondent on Twitter here. You could also follow a live blog from the Spain Report here. The official results are expected to be published by the interior ministry here. Polls are scheduled to open at 9 a.m. local time and close at 8 p.m. local time. Exit-poll results are expected shortly thereafter.