Marin Cilic and Borna Coric both won their singles matches to put Croatia 2-0 up in the Davis Cup final against hosts France.
Cilic, the world number seven, easily got the better of the injury-hit Jo-Wilfried Tsonga 6-3 7-5 6-4.
Tsonga, who needed a medical time out in the third set, missed all five of his break-point chances.
Earlier, Coric, ranked 12, defeated world number 40 Jeremy Chardy 6-2 7-5 6-4 to give Croatia the advantage.
Coric broke serve in the first game and stayed in control in the tie at Lille’s Stade Pierre Mauroy.
France captain Yannick Noah sprang a surprise by opting for Chardy for the opening singles rather than Lucas Pouille, the highest-ranked player in his squad.
But the gamble backfired with Coric, who has had the best season of his career, storming into a 4-0 lead on his way to winning the opening set.
Chardy fought back in the second set and led 5-4 but Coric held his nerve to break his opponent and take the set.
The Croatian needed a brief medical time-out when he led 4-3 in the third set but returned to complete a convincing win.
France will need to win Saturday’s doubles which will see French Open doubles champions Pierre-Hugues Herbert and Nicolas Mahut up against Mate Pavic and Ivan Dodig.
Victory for Croatia would give them their second Davis Cup crown in the final staging of the historic team competition before the format changes next year.