[Update: The best analysis of the results I've found comes from an essay in Slate, that actually appeared yesterday (before the results were known). Obviously more in-depth analyses will be appearing in the weeks to come, but right now the best explanation on the block is the rural/urban divide.]
In a huge upset, the Congress party has won the elections. Will Sonia Gandhi be the next PM?
According to SoniaGandhi.org, Sonia is actually the third foreign-born woman, and the eight person overall to be the president of the Congress party. The other two foreign-born women were Annie Besant (the famous reformer and theosophist) and Nelli Sengupta.
So she is no anomaly in a certain respect. But neither of those other women were President of Congress in independent India. A foreign-born Prime Minister would definitely be completely unprecedented, in Indian history as well as the histories of many other Parliamentary republics. It would also be a constant liability for the Congress.
Interestingly, one of the other possible names mentioned as a Prime Minister candidate is Manmohan Singh. It seems unlikely (where has he been for the last 10 years?), but he is often credited with starting India down the path of liberalization in the early 1990s, so he might be reassuring to the business community.
Another name is Harkrishan Singh Surjeet, the head of the Communist Party. Other names are Deve Gowda (who was the head of the United Front governemnt in 1996), as well as Laloo Prasad Yadav (the notoriously corrupt minister from Bihar).
Doesn't look like too many good options! I think Sonia is inevitable.