Tamil Nadu Chief Minister K Palaniswami hinted that AIADMK may not back the no-confidence motion while the BJD and the TRS have not made their stand clear yet.
The debate is scheduled to last for seven hours followed by Prime Minister Narendra Modi's reply, which is expected at around 6 pm, official sources said. The debate timing in Parliament is, though, often stretched beyond the scheduled duration.
The BJP is likely to pit a clever mix of speakers representing different constituencies of voters to express its views and some ministers may also intervene, sources said.
Kumar said the Opposition will be no match to the BJP's top guns led by Modi and took a dig at it, saying it should not "talk out" of the debate as it will be left wondering if it made the right move by pushing the no-confidence motion.
With the BJP already in campaign mode and Modi addressing rallies in different parts of the country, the party believes his reply will give impetus to its election drive. The next Lok Sabha polls are less than 10 months away.
Kumar also pooh-poohed Congress leader Sonia Gandhi's suggestion that the Opposition has numbers to back the motion, saying her maths is weak.
He recalled that she had made the claim of having support of 272 members after the Vajpayee government had fallen in 1999 by losing the vote of confidence by merely one vote.
"She is repeating history after almost 20 years. She will get to know tomorrow where the Opposition and the BJP stand," he said.
On the debate eve, the BJP also engaged in dinner exercise with its whips hosting many groups of party MPs.
Its dissident MP Shatrughan Sinha also announced his support to the government. Suspended BJP MP Kirti Azad is unlikely to be present due to personal reasons.