The electoral arithmetic of Modi's bid for PM

Ashutosh Varshney, professor at Brown University, has done the Math on what it would take Modi to become PM in this article in IE:

When the BJP won 182 seats in 1998 and 1999, it captured 25.6 and 23.7 per cent of the national vote respectively. In 2009, it won a mere 18.8 per cent (and 116 seats). Though, under certain exceptional circumstances, one can show that a party can win 180 seats in India's Parliament with only 18-20 per cent of the national vote, a more reasonable assumption is that 24-25 per cent of the national vote will, in all probability, be required for 180-plus seats. In short, Modi needs to raise the BJP's vote by 5-6 percentage points.
In 2014, the size of the electorate is expected to be a little over 800 million. Assuming a 60-62 per cent turnout, we will have roughly 500 million voters. A 5-6 per cent increase in the BJP's vote essentially means that Modi will have to deliver an additional 25-30 million votes .

Varshney is sceptical about Modi being able to bring it off in 2014:

Of the 500 million likely voters in 2014, only 150 million will be urban, and of these, only 90 million are in the west and north. The BJP has already won a lot of these votes in the previous elections. Can Modi really mobilise an additional 20-25 million votes from this northern and western pool, assuming he can get 5 million more elsewhere? 

The order is monumentally tall. Advani may well have the last laugh next year unless a broad anti-Congress alliance can be constructed. With urban India rising, Modi's power to pull votes could be greater in the 2019 or 2024 elections, but might fall well short in 2014.