In the biggest embarrassment for the Congress, Chief Minister Virbhadra Singh's wife and sitting MP from Mandi Lok Sabha seat, Pratibha Singh, was defeated by BJP's greenhorn Ram Swaroop Sharma. Sharma defeated Pratibha Singh by a margin of 39,796 votes, an election official said.
In the 2013 bypoll, Pratibha Singh won from the seat by a margin of 136,724 votes. The seat was vacated by Virbhadra Singh after he assumed charge as the chief minister.
The Bharatiya Janata Party (BJP) candidates won the other three Lok Sabha seats in the state with record margins.
As per the trend emerging in two decades, the electorate in the Lok Sabha polls has traditionally favoured the party at the helm in the state.
"It is for the first time in the history of Himachal that the ruling party of state could not enjoy any advantage and faced crushing defeat after just over one and half years of helm in the state," said a political observer.
A senior Congress leader said Pratibha Singh's defeat was a setback for Virbhadra Singh's "succession plan".
"Virbhadra Singh was keen to ensure the victory of his wife at this point in time when his son was not eligible to contest the poll because of his underage," he said.
The Congress has a thin majority with 36 seats in the 68-member House, though it has roped in four independents. The Bharatiya Janata Party (BJP) is not far behind with 26 seats.
In 2009, the BJP, which was then in power in the state, won three of the four Lok Sabha seats.
"It's was simply a Modi wave that went in the favour of the (opposition) BJP," Virbhadra Singh told reporters in Shimla.
He ruled out his resignation over his party's poll defeat.
When asked that Assam Chief Minister Tarun Gogoi offered to resign, taking moral responsibility for the defeat, Virbhadra Singh said: "He may have some compulsions but I don't have any compulsions."
Former union minister and two-time BJP chief minister Shanta Kumar emerged victorious with a margin of 1.70 lakh votes.
In the prestigeous Mandi seat, all eyes were on Hamirpur seat that witnessed a battle of supremacy between archrivals Virbhadra Singh and Prem Kumar Dhumal. In the parliamentary elections, development and corruption were pushed to the background as personal attacks dominated.
Dhumal's son Anurag Thakur re-contested in Hamirpur, a BJP bastion, and won by margin of over 95,000 votes.
Thakur, who is also the president of the Himachal Pradesh Cricket Association (HPCA), hit a "hat-trick".
Virbhadra Singh, a star campaigner, has travelled across the state but Dhumal concentrated his campaign mainly in Hamirpur as his son drew flak for his high-profile lifestyle.
To challenge Thakur, 39, who was recognised as the Young Global Leader 2014 by the World Economic Forum, the Congress fielded his father's protege Rajinder Rana, 48.
The chief minister is said to have asserted that Rana was the best choice, as besides his popularity, he knows the Dhumal family inside out. "But Virbhadra Singh failed on this front too," said a political observer.
BJP's outgoing MP from Kangra, Rajan Sushant, 58, who had joined the Aam Aadmi Party (AAP) after a prolonged tussle with the state party, faced a humiliating defeat.
The Congress was in troubled waters in the Shimla (reserved) seat as it faced defeat. For the first time in 2009, the BJP managed to win this seat, which was considered a Congress bastion.
BJP's sitting MP Virender Kashyap, 63, who was booked in March on a corruption charge, won the seat by over 80,000 votes.