Supporters of Congress's Delhi Chief Minister Sheila Dikshit celebrate
India's governing Congress Party has won three of the five states where elections were held recently, final results there show.
Congress won in Delhi, Rajasthan and Mizoram while the main opposition BJP was poised to retain Madhya Pradesh and Chhattisgarh in central India.
The key election issues had been the economic slowdown and security following the Mumbai (Bombay) attacks.
The votes come ahead of a general election, which must be held by May.
The BBC's Sanjoy Majumder in Delhi says many had expected Congress to be on the receiving end of a backlash following the Mumbai attacks and amid economic uncertainty.
But the Hindu nationalist Bharatiya Janata Party has lost Rajasthan by 96 seats to 78 and Delhi by 42 to 23.
The BJP was well ahead in Madhya Pradesh and also likely to retain control in Chhattisgarh where the contest was closer. Final results were due later on Monday.
In Mizoram in the north-east, Congress swept back to power for the first time in a decade. It won 32 of the 40 seats.
Our correspondent says this is a morale-boosting performance for the government.
He says Congress is particularly celebrating the result in Delhi - a third straight term in a state that voted in the immediate aftermath of Mumbai, when the government was being strongly criticised for being weak on terrorism.
"This is the beginning of the decline of the BJP," Congress spokesman Veerappa Moily told the Reuters news agency.
Delhi Chief Minister Sheila Dikshit condemned the BJP for playing the "terror card".
"It's an outright rejection," she said. "The people of Delhi have given a fitting reply."
BJP president Rajnath Singh admitted defeat in Delhi was "shocking as we thought we would win".
Voting in Indian-administered Kashmir is still going on and the results for the state of Jammu and Kashmir will be released later in December.
Along with rising prices, security has been a key issue in the six elections, with many Indian cities, including Mumbai, Bangalore, Jaipur, Ahmedabad and Delhi hit by bomb blasts recently, with large loss of life.
The BJP campaigned for a tougher anti-terror law.
Analysts had said the party that fared better would find it easier to secure alliances with regional parties before the general election, which is of the utmost importance when building a post-election governing coalition.