Members of Israel's ruling Kadima party were voting Wednesday on their centrist movement's list of parliamentary candidates, some eight weeks before the Israeli elections, dpa reported.
Results were not expected until early Thursday morning.
As she cast her vote Wednesday morning in Tel Aviv, Israeli Foreign Minister Tzipi Livni said: "We will choose a list and with it we will win."
Livni, who who was elected party leader in a separate vote in September, added she had "faith that each of Kadima's members wants to see a list that is best for the state, and so it will be."
Some 80,000 registered Kadima members were eligible to vote in Wednesday's primary. Polling booths opened at 10 am (0800 GMT) in 95 stations throughout the country and were scheduled to close at midnight.
Livni has been losing ground to opposition leader Benjamin Netanyahu of the hardline Likud party in recent opinion polls. Both the Likud and the left-to-centre Labour Party of Defence Minister Ehud Barak already chose their lists for the February 10 elections earlier this month.
The elections in Israel are being held just over a year ahead of schedule and follow on the resignation of caretaker Prime Minister Ehud Olmert in September amid corruption allegations.