Spain are on the verge of winning the Davis Cup after opening day victories for Rafael Nadal and David Ferrer left Argentina teetering on the brink.
Nadal thrashed Juan Monaco before David Ferrer beat Juan Martin Del Potro in an energy-sapping five-set epic.
Ferrer's victory - which took nearly five hours to complete - sent the 28,000 crowd in Seville into raptures.
It means Spain only need to win one of the three remaining matches over the weekend to take the crown.
After his comfortable 6-1 6-1 6-2 victory, Nadal - who complained of fatigue after his early exit last week at the ATP World Tour Finals in London - said: "To win by such a score against a very strong player is fabulous.
"I played a very solid match and I am very happy with my performance," added Nadal, whose only defeat in 20 Davis Cup singles matches on all surfaces came in February 2004 against Czech Jiri Novak.
"I was very positive before the match even if there was a lot of pressure. It's an important victory. I was sad for him as he is one of my best friends."
World number five Ferrer then went on to defeat Del Potro 6-2 6-7 (2-7) 3-6 6-4 6-3.
Ferrer said: "I played maybe the best match of my career, I am very happy.
"Now I am very tired because it was very close. The first set I was very tired but he was worse then me.
"I played very consistently all the match. We want to enjoy this moment and relax."
The final is a repeat of 2008, when Spain won on a hard indoor surface in Argentina despite missing Nadal because of injury.
Argentina are seeking a first title in four attempts, having finished runners-up in 1981, 2006 and 2008, while Spain have won it on four occasions - 2000, 2004, 2008 and 2009.