Raonic overcame the loss of a first-set tiebreak to defeat Albert Ramos 6-7 (5-7), 6-4, 6-4, 6-4, and Dancevic coasted past Marcel Granollers 6-1, 6-2, 6-2.
Canada will try to wrap up the best-of-five match series Saturday when its doubles team of Daniel Nestor and Vasek Pospisil take on Granollers and Marc Lopez.
The winner of this matchup will meet either Italy or Croatia in the quarterfinals, which will be played in April. The Italy-Croatia matchup was tied at 1-1 after Friday's action.
Raonic served 26 aces, twice as many as Ramos, and produced 78 winners to 36 errors. Dancevic needed just 108 minutes to dispose of Granollers.
These countries have met once before in Davis Cup play with Spain having won that confrontation.