Immediately after french revolution, a National assembly was created to manage the state. In the chamber were the members of the religious clergy, Nobles(Conservative in thought,  with feudal outlook) and  also the new revolutionaries (labourers/wage earners who more liberal, less religious). They were known as First Estate (Clergy), second Estate (Nobles) and third Estate (Revolutionaries) estates respectively.
They were seated such that Nobles and Clergy were on the right side and the  revolutionaries on the left side.

Even to-date parties with religious/feudal & conservative outlook are called as rightist parties, and the ones that are less religious and more representing workers & peasants as Leftists.

The events of past week have been fascinating. Congress has been given an mandate to have a decisive rule for next 5 years. I feel this again reinforces the Indian voters general centrist thinking, which doesn’t want extreme leftism or extreme rightism in polity. The only time when BJP could come to power was when Vajpayee projected a more centrist views. The only time Left smelled power (other than the blackmailing they did in past 5 years) is when Harkishen singh surjeet and Jyoti basu were more pragmatic and were willing to tow a centrist approach.
Mr. Karat and Mr. Advani made a huge errors when they thought their ideological extreme would enthuse Indian voters. As a traditional BJP voter, I keep hearing murmurs within BJP that it should go back to its roots (that is to say – more religiousity and more RSS). I always felt that would be a mistke as BJP only became an acceptable ruling party when it shed the hardline Hindutva. BJP won’t get anywhere near all India power, if it backs (even implicitly) the ‘crazies’ like Mutalik or Varun gandhi.

Similarly, Congress will loose heavily if it tries to move away from centrist line and leans towards Muslim Appeasement. Its hard days began immediately after the Sha-bano episode, and led to the gain of then more centrist BJP.

People keep berating Urban Middle-class for not voting, thus yielding the political initiative to rural India. But, amazingly Indian electorate (Urban or rural), seem to vote more and more for same issues. Development, Peace and Stability. Atleast in past half dozen years, election after election, the Leftist and Rightist moorings are finding less takers.
India will continue to be a centrist, secular nation. Hope BJP realizes that and bounces back, because India certainly needs a right of center party to balance the left-of-center Congress.
The left parties will not be able to survive for long with their Ideology. If they dump their extreme ideology, there will be no difference between them and dozen other parties in India. Soon, someone else will take over their voters. Tough choice indeed.