"It's the prediction that the president might likely get 70 to 75 percent," ZANU-PF spokesman Rugare Gumbo said, adding early results showed a strong lead for the 89-year-old veteran.
Official results from Wednesday's presidential election have not yet been released, but Gumbo said tallies posted at some polling stations had showed a landslide for Mugabe.
"It's the feel. From what I see what is happening on the ground," he said.
With about a third of the national assembly results released, Gumbo was also confident the party would achieve a two-thirds majority in the 210-seat house.
"We can't get less than 130, 140 seats. I'm sure will get there. I think we are going to get about two-thirds majority."
The first official results showed Mugabe's party storming ahead, winning 52 of the 62 seats announced.
Tsvangirai, who is making his third bid to end 89-year-old Mugabe's 33-year rule, has slammed the vote as a "huge farce."
BA/