Israeli Prime Minister Benjamin Netanyahu has claimed a "huge win" in a vote that challenged his leadership of the Likud party.
Mr Netanyahu secured 72.5% as opposed to his rival Gideon Saar, who polled 27.5%.
Mr Saar admitted defeat, saying he would now back Mr Netanyahu in a general election due in March.
The internal party vote was seen as a test of Mr Netanyahu's hold on power at a time of mounting difficulties.
Mr Netanyahu, 70, faces trial on bribery and corruption charges, as well as a third national election within a year.
Previous elections held in April and September saw Likud deadlocked with the centrist Blue and White party - with neither able to form a government.
"Huge victory!" Mr Netanyahu tweeted. "Thank you Likud members for the vote of confidence, support and love. God willing and with your help, I will lead the Likud to a great victory in the upcoming elections and will continue to lead the state of Israel to unprecedented achievements."
Mr Saar, a 53-year-old former minister in Mr Netanyahu's cabinets, conceded defeat.
"I am content with my decision to have stood," he tweeted. "Those who are unwilling to take a risk for what they believe in will never succeed.
"My colleagues and I will stand behind [Netanyahu] in campaigning for the Likud's success in the general elections," he added.
Mr Saar, a well-known figure in the party, had warned that Likud would not win the forthcoming elections under Mr Netanyahu.
Benjamin Netanyahu had been expected to win comfortably but campaigned tirelessly because he wanted the result to show his grip on the party remained strong, the BBC's Barbara Plett Usher in Jerusalem says.
Mr Netanyahu, who is the country's longest serving leader, is facing mounting difficulties after being indicted in three corruption cases last month.
He denies wrongdoing and claims the charges are a politically motivated "witch-hunt" against him.