Until someone (Sujeet?) from India wakes up to offer more detailed analyses, I will venture some thoughts: I am somewhat surprised by how big a win the Congress achieved. The accepted post-mortem is that the BJP erred on pushing hard on their security/hindutva agenda, some of the response to the Bombay terrorism, the anti-Muslim statements by Varun Gandhi (no real relation to Mahatma Gandhi), the prominence of Narendra Modi (the architect/leader of government of/during the pogrom in Gujarat) etc. At the same time, Congress has (or seems to have) come to own the rural unrest issue, both because the rural neglect and IT coddling flowered under the BJP and the Congress has initiated various measures (such as cancellation of farmer debt) since they regained power.
As I wrote, there are some parallels between the BJP and the GOP both of which built their base using fear and religion, with a dollop of free market individualism, and they are hitting the same ceilings: the yuppie urban younger crowd probably finds the BJP icky, and the rural discontent cannot be overcome via religious false issues in a country lacking any safety net. There are parallels as well between the Dems (culminating in the Obama phenomenon), where the rise of the BJP and the death of the JP and its offshoots, provided a neat space for the Congress to take on the image of a kinder, gentler, secular neo- liberal party.
All IMHO,
--ravi