In warm winter sunshine outside a polling station in Har Homa, an Israeli settlement south of Jerusalem, Yoni Shetbon was confident that by morning he would be one of Israel's 120 MKs (members of parliament).

But at number 11 on the Jewish Home party's list of candidates, the next few hours will be nerve-racking for the young pro-settler activist. Opinion surveys have forecast that the hardline ultra-nationalist party will win around 12 seats in the next Knesset, but with 18% of Israeli voters still undecided by the time the polls opened on Tuesday morning, predictions could be wide of the mark.

Shetbon said public support for his party's relentless message about "Jewish values" and its total rejection of a Palestinian state in the West Bank would translate to a strong showing in the election. "We are not extreme, we are actually at the centre of public opinion in Israel. What we say is what people think. We will have more than 12 [MKs], with the help of God," he said.

Hannah Finkelstein, 35, had cast her vote for Jewish Home. "I chose Naftali Bennett, even though every time before I have voted for Likud. But this is an opportunity for the national-religious people to influence the government," she said, referring to Israeli Jews who believe their right to settle the land in the West Bank is God-given.

Her views were echoed by Miriam, 38, who said she voted for Bennett because of the need to expand the Jewish presence in the West Bank. Her husband, Shlomo, 41, said he had a "big hesitation" before casting his vote but in the end chose Strong Israel, a small party even further to the right, which may not cross the 2% threshold of votes required to win a parliamentary seat. "In the end I voted for the one I really believe in, the party that is more rightwing [than Bennett's] and less likely to make concessions to the Palestinians."

In a straw poll in Har Homa, rightwing voters were in a clear majority. But Mili, 30, said she had voted for Labour "because I don't like Netanyahu and Shelly [Yachimovich, the Labour leader] has the power to be a strong opposition". And Joel, who came to Israel from Ethiopia 15 years ago, was backing the centrist Yesh Atid party because of its agenda to improve socio-economic conditions, especially housing.

By 4pm (1400 GMT), the Central Elections Committee said 46.6% of eligible voters had turned out, up from 41.9% at the same time in the 2009 election. But voter turnout in Arab areas was reported to be much lower, averaging around 10% by midday.

In Beit Safafa, an Arab neighbourhood in south Jerusalem, Huda Hussein, 56, said: "I voted for [Haneen] Zoabi [of the Israeli-Arab party Balad] because I like her, she helps people, she's strong in the Knesset, and she's a woman – and that's important."

Rushdi Alian, 26, a keeper at the nearby Jerusalem zoo, dismissed arguments that Arab citizens of Israel should boycott the election. "I think it's important that Arabs are in the Knesset. Most people in this village are voting." He had backed Raam-Taal, led by Ahmed Tibi. "He is always fighting for the Arabs," said Alian. "We need strong people like Tibi to face politicians like Bennett."