Jerusalem (CNN) In 1988, extremist Rabbi Meir Kahane and his political party were banned from Israel's parliament for being racist and undemocratic. Now his followers are making a comeback, courted by Prime Minister Benjamin Netanyahu as he seeks a fifth term as the country's leader.

On Tuesday night, Netanyahu tweeted directly at two right-wing parties and the extreme right Jewish Strength party.

"The head of the Jewish Home, the National Union, and Jewish Strength -- if you don't unite, you won't pass the electoral threshold, the right-wing bloc will lose and Gantz will form a left-wing government with the support of the Arab parties," he wrote.

"Right-wing voters expect from you to show responsibility and to unite. Do not disappoint them and do not endanger the land of Israel," he added.

Rabbi Meir Kahane and his political party were banned from Israel's parliament for being racist and undemocratic.

The extreme right Jewish Strength party, called Otzma Yehudit in Hebrew, is made up of followers of extremist Rabbi Meir Kahane, whose anti-Arab Kach party was banned four years after it entered the Knesset in 1984. Kahane's speeches were boycotted by every other party. In 1994, it was banned outright in Israel under anti-terror laws. Three years later, it was designated a terror organization in the United States.

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