Spain votes in a major election that could bring the far right back to power

Spain voters are heading to the polls on Sunday in an election that could bring the far right to power for the first time since Francisco Franco's dictatorship.

Polls published ahead of the vote projected a conservative win, with the PP (Partido Popular) set to secure about 34% of support — which would not be sufficient to form a majority government.

Some political analysts expect PP to join forces with the far right party Vox, which could be the third biggest political force in this election and obtain more than 10% of the votes.

"The most likely outcome is a coalition government with PP firmly in the lead and in control of most key ministries, and Vox as the junior partner," Federico Santi, senior analyst at Eurasia Group, said in a note Wednesday.

He added that this scenario "would be moderately market-positive, as reflected in Spanish asset prices over the last few weeks, with a modest outperformance of Spanish equity indices compared to European peers, while the sovereign credit spread vis-à-vis Germany has remained broadly stable."

The conservative party PP and the far right Vox have previously made political agreements to govern in three of Spain's regional authorities and have other accords in smaller cities.

However, their relationship seems more of a forced cohabitation than a natural partnership.

In a TV debate ahead of the elections, PP leader Alberto Feijóo indicated that he would govern with Vox, if he needed their votes. Members of the conservative party have raised concerns regarding Vox's anti-LGBT rights and anti-immigration policies.

Vox has also been criticized by mainstream politicians for opposing abortion rights and denying climate change, among other measures.

When debating against incumbent socialist leader Pedro Sanchez, Feijóo said that his rival could not lecture other politicians on pacts. Sanchez made agreements with separatist parties to secure a working parliamentary majority.

Tacho Rufino, economist at the University of Seville, told CNBC's Charlotte Reed on Thursday that this election is less about economic than cultural matters — including nationalism, LGBT rights, and climate change.

For his part, Sanchez has been criticized for pardoning politicians supporting regional independence, for instance. During his mandate, there have also been issues with the "only yes means yes" sexual consent law, which reduced the serving time for many convicted rapists through a loophole.

The Sunday vote might also be impacted by climate change, as this is the first election to take place during the summertime. Spain is one of the southern European nations that's been through a significant heatwave in recent days.