NEW DELHI (Reuters) - Indian Prime Minister Narendra Modi’s ruling group will sweep an election in his home state of Gujarat, surveys showed on Thursday, shaking off the most serious challenge yet from a combined opposition.

India's Prime Minister Narendra Modi shows his ink-marked finger after casting his vote outside a polling station during the last phase of Gujarat state assembly election in Ahmedabad, India, December 14, 2017. REUTERS/Amit Dave

The election for a new state assembly in Gujarat is seen as a litmus test for Modi ahead of a national election in 2019. Voting closed on Thursday.

A win would help him dismiss critics who said the ruling Bharatiya Janata Party’s support base was eroding after last year’s shock move to ban high-value currency notes in the fight against graft, and poor implementation of a national sales tax this year hit businesses.

The Congress party led by Rahul Gandhi and teaming up with regional politicians has run a tough campaign aiming to weaken Modi in his home base and rouse public discontent over lack of jobs and a softening economy.

But three separate television exit polls at the close of the final round of voting on Thursday showed the BJP winning more than 100 seats in the 182-member state house, well clear of the half-way mark of 92 required to rule.

Congress, the main opposition party, will win 70-74 seats, the polls showed, better than in the past but not enough to oust the BJP from power.

Another exit poll, conducted by a Today’s Chanakya group, gave the BJP a two-thirds victory.

The actual votes will be counted on Monday and exit polls and other surveys have often gone wrong in India, where millions vote. The Congress party said it was too quick to call the election based on exit polls.

The BJP has ruled Gujarat since 1998, with Modi as its chief minister for more than a decade before he became prime minister three years ago.

Modi has won praise for transforming the coastal state into an economic powerhouse and deploying business-friendly policies to lure foreign investors.

To ensure his party’s prospects, Modi led from the front to campaign in the state and addressed dozens of public rallies, performed rituals and even waved from a sea plane on the last day of his campaign trail.

On Thursday, Modi cast his ballot in Gujarat’s Ahmedabad city and then hit the streets again, showing off his inked finger as he walked, surrounded by hundreds of supporters.

In separate exit surveys released for state polls held in Himachal Pradesh state also showed Modi’s party emerging as a winner.