Article published on the 2008-07-22 Latest update 2008-07-22 08:18 TU
"It is a tight race, no doubt about that," analyst and opinion pollster Yashwant Deshmukh told AFP.
"The government would never have gone for the vote if they were not sure of winning," he said.
A bloc of left-wing and communist parties pulled their support for Singh in protest over the nuclear deal with Washington which was designed to bring India into nuclear commerce after decades of isolation.
India has nuclear weapons and refuses to sign the nuclear Non-Proliferation Treaty. The deal is to be treated as a special case on condition it separates its civil and military programmes and allows some UN inspections.
Government officials defended the deal during Monday's parliamentary debate, arguing that the country's 1.1 billion people need alternative sources of energy to avert an impending fuel crunch.
Officials argue India's power stations cannot keep up with demand, that coal is running out, and power cuts are frequent not the recipe for continued strong growth of more than nine percent.