The poll on Friday said Vajpayee's regional partners in India's south and east had lost ground and his own Hindu nationalist Bharatiya Janata Party (BJP) had failed to improve its showing in the key heartland state of Uttar Pradesh which starts voting on 26 April.
The main opposition Congress led by Sonia Gandhi, the torchbearer of the celebrated Nehru-Gandhi dynasty, had picked up momentum after a listless start, but was still far behind the ruling coalition, the Indian Express-NDTV poll said.
Just over a quarter of India's electorate of 670 million has voted in the first two phases of the poll, which moves on Monday to Uttar Pradesh which, along with neighbouring Bihar, has traditionally held the key to power in New Delhi.
"The battle now is really on and the alliance needs to do really well in the next two rounds of polling to cross the half-way mark"
The ruling BJP-led alliance which has campaigned on a platform of peace and prosperity, could win anything between 255 to 275 seats in the 545-member lower house of parliament, the poll said.
The coalition won 306 seats in the last election in 1999, comfortably higher than the 273 required to rule.
"The battle now is really on and the alliance needs to do really well in the next two rounds of polling to cross the half-way mark," the Indian Express said.
Analysts say the BJP-led coalition will still be the best-placed to form a government by attracting smaller parties to its fold but would face pressures from these parties, including on key reforms such as labour laws.
India's financial markets which have soared in the past year on the back of reforms and strong economic growth are banking on a convincing win for the BJP-led coalition to push through reforms more aggressively.
The BJP has played down its hardline Hindu image and has campaigned on a slogan of a "Shining India" buoyed by bumper harvests, cheap loans and peace with Pakistan.
The Congress says the average Indian has not benefitted from the economic liberalisation and accuses the BJP of hurting India's secular foundations.
Votes will be counted on 13 May and the results are expected the same day.