JERUSALEM (Reuters) - Discontent over a ceasefire that Israeli Prime Minister Benjamin Netanyahu struck with Hamas in Gaza has cost him support before an election in January but he should still win the ballot, a poll showed on Friday.

The survey by Israel's Maariv newspaper, the first since the truce took hold on Wednesday, said the newly merged party of Netanyahu and Foreign Minister Avigdor Lieberman, Likud Beitenu, would take 37 of the 120 parliamentary seats up for grabs on January 22. A poll taken before the eight-day conflict suggested they would win 43 seats.

It said that 31 percent of Israelis approved of the ceasefire while 49 percent were opposed. Asked if the army should have re-occupied Gaza, 41 percent were against and 29 percent in favor.

The poll has a 4.5 percent error margin.

(Writing by Maayan Lubell; Editing by Angus MacSwan)