Both the conservative Popular Party (PP) and the socialist PSOE received a boost in polling support since the Paris attacks on November 13th, according to a survey on Monday by consulting firm GAD3 for ABC.
The latest poll was conducted on November 20th and compares to a survey carried out on November 13th, before the attacks.
The PP saw an increase of two more parliament seats compared to before the attacks while the PSOE saw an increase of four more seats.
The PP remained on top of the polls with 28.5 percent of respondents and 129 seats, while PSOE came in second with 22.8 percent of respondents' votes and 93 seats. Ciudadanos followed behind at 16.4 percent of respondents and 52 seats.
Together the PP and the PSOE would receive two-thirds of the seats in parliament based on the poll results.
ABC attributed the increased support to concerns about the Paris attacks, noting that these two parties are the only ones with "governing experience".
Both parties had previously seen their support fall between a poll on November 5th and the poll on November 13th.
According to GAD3, voters are still primarily concerned about the economy and unemployment, but over the past week, security has become more important than the Catalan independence issue. And concerns about security tend to benefit parties with more experience.
Still, anti-austerity party Podemos - which only started last year - also saw gains in the latest poll. The left-wing party saw an increase of seven seats compared to the last poll and received 15.6 of the vote from respondents.
Ciudadanos (Citizens), which was formed as a regional Catalan party in 2006 but expanded nationally earlier this year, saw a fall of four seats.
King Felipe VI has reportedly warned both PP's Prime Minister Mariano Rajoy and PSOE's leader Pedro Sánchez against using renewed fears of terrorism as a political tool ahead of the election on December 20th, according to El Confidencial Digital.
According to the digital newspaper, the king did not want to repeat what happened after the 2004 Madrid train bombings, attacks which killed 191 people three days before the general elections.
After the 2004 attacks, in-fighting broke out among the parties over which terror organization was responsible with the PP government blaming Basque nationalists ETA, even with evidence that an al-Qaeda inspired group was responsible.
King Felipe has asked both party leaders now to meet as often as possible to maintain a dialogue about security matters. Rajoy has already reportedly invited Sánchez to have such talks and they are also talking by phone regularly.