Marin Cilic excelled at doubles duty with Ivan Dodig as the Croatian pair defeated Argentines Juan Martin del Potro and Leonardo Mayer 7-6 (7-2) 7-6 (7-4) 6-3 to hand the hosts a 2-1 lead in the Davis Cup final on Saturday.
One more victory in Sunday's reverse singles would earn the Balkan nation a second title in the worldwide team competition after a first trophy in 2005.
Cilic started the weekend tie on Friday by beating Federico Delbonis as Argentina got off on the wrong foot in their bid to win a Davis title after losses in four finals.
Cilic and Dodig showed the value of Davis Cup experience as they dispatched the visitors.
The win coming on the back of other David Cup doubles victories over Americans Bob and Mike Bryan and the French pair of Pierre-Hugues Herbert and Nicolas Mahut earlier in the competition.
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"This point was crucial because now comes the match for Marin, we needed to win yes or yes," Dodig said.
Top players Cilic and del Potro will meet on Sunday in singles.
"Juan Martin and I are in the same situation, we will be at the same level," Cilic said after both won on Friday.
"Today Juan Martin played well, every game we played was very close."
Watched by the country's president, Croatia won the doubles rubber in just under two and three-quarter hours with 33 winners and 42 unforced errors in the tight contest. Del Potro and Mayer kept their error count to a modest 34 in the losing effort.
