* Modi's party set to beat Congress, but short of majority
* Modi set to win 188 of 543 seats in parliament-poll
By Shyamantha Asokan
NEW DELHI, Jan 23 (Reuters) - The opposition Hindu nationalist party of Indian prime ministerial hopeful Narendra Modi is on course to emerge the biggest in general elections due by May, two opinion polls showed on Thursday.
Modi's Bharatiya Janata Party (BJP) is set to win 188 seats in the 543-seat parliament, over twice the predicted tally of the Congress party of outgoing Prime Minister Manmohan Singh, according to a poll on Thursday by pollsters CVoter and the India Today media group.
Given India's diverse and fragmented electorate, neither the BJP nor any other party is expected to win the 272 seats needed for an outright majority. The biggest party will seek to form a coalition with regional parties.
The Congress party, which has yet to name its prime ministerial candidate, faces an uphill struggle this year due to public anger over a string of corruption scandals and economic growth hitting a decade-low.
Another poll forecast that the BJP would win the lion's share of the vote in many of the big states that typically decide the fate of Indian elections.
The party is forecast to win 41-49 of the 80 seats in Uttar Pradesh, India's most populous state and home to 200 million people, according to a survey by pollsters CSDS and the CNN-IBN news channel, the results of which were released in stages this week.
It is also predicted to emerge as the largest group in Bihar, with 16-24 of the state's 40 seats, and to win well over half of the 48 seats in Maharashtra along with a long-term ally. Maharashtra is home to India's financial capital Mumbai.
Modi, who has presided over rapid economic growth during more than 12 years as the chief minister of the state of Gujarat, has been wooing voters by pointing to his track record as a leader who cuts red tape and attracts investment.
"People have already decided the outcome of the election. Congress-free India will be a reality," Modi said at a packed rally in Uttar Pradesh on Thursday, where his podium was decorated with floral garlands.
Congress has decided not to name its prime ministerial candidate until after the elections even though many party workers had wanted Rahul Gandhi, the scion of the Nehru-Gandhi dynasty that leads the party, to take on the role.
"Three to four months back, people were saying this would be a presidential-style race between Modi and Rahul Gandhi," said CSDS director Sanjay Kumar. "Now things have changed, now it's not a presidential race - it is a referendum on Modi."
CVoter surveyed almost 21,800 respondents across India's 28 states, with a three per cent margin of error at the national level. The CSDS poll surveyed just under 18,600 voters in 18 states, with a margin of error that varies from state to state. It will issue a national projection on Friday.
One factor that could upset these forecasts is the rise of the Aam Aadmi Party, or Common Man Party, a new anti-graft group that claimed a surprise victory in local elections in Delhi last month and has since decided to take part in the national polls.
The CVoter survey forecast that the new party would win 10 seats in the national polls.
"I think they will have an impact in northern India and the cities, but it's too early to say to what extent," said Neerja Chowdhury, a political analyst and a former political editor of the Indian Express newspaper.
While Modi has a strong showing in the polls, he could struggle to find coalition allies as his image remains tarnished by communal riots in Gujarat 12 years ago, in which more than 1,000 people were killed, most of them Muslims.
Modi has denied that he failed to stop the violence and a Supreme Court inquiry found no evidence to prosecute him.
"If the BJP crosses the magic number of 182, Modi should be able to do it," said Chowdhury, referring to the 182 seats that the BJP won when it last formed a coalition government in 1999.
India's diverse political landscape makes election results notoriously hard to forecast, particularly in terms of how many seats a party might win, versus the more straightforward calculation of a party's share of the overall vote. (Additional reporting by Frank Jack Daniel and Malini Menon in NEW DELHI)