Of them, two each are from the Congress (M. Veerappa Moily and N. Dharam Singh), the BJP (B.S. Yeddyurappa and D.V. Sadananda Gowda) and the Janata Dal-Secular (JD-S) H.D. Deve Gowda and his son H.D. Kumaraswamy.
Moily is the central minister for petroleum and natural gas in the outgoing UPA-II government.
Gowda had been chief minister for 18 months from December 1994 to May 1996 when he was catapulted to the prime minister's office after prime minster Atal Bihari Vajpayee quit after 13 days in office.
Barring Yeddyurappa, the other five have been parliamentarians, with Moily, Singh and Gowda being outgoing members and seeking re-election from their constituencies: Chikkaballapur, Bidar and Hassan.
Sadananda Gowda and Kumaraswamy, elected from Udupi-Chikmagalur and Bangalore Rural in 2009, could not complete their term as they quit to enter the state legislature.
Sadananda Gowda had to quit the Lok Sabha in September 2011 after he became the BJP's second chief minister a month earlier and got elected to the state legislative council.
Similarly, Kumaraswamy gave up the parliamentary seat in June 2013 following his election to the state assembly from Ramanagara, about 50 km from here.
Ironically, both the parties (BJP and JD-S) lost to the Congress in the bye-elections of 2011 and 2013, reducing their tally in the Lok Sabha.
The BJP bagged 19 of the 28 parliamentary seats in the state in 2009 while the Congress got six and the JD-S three.
Returning to the BJP after damaging its prospects in the May 2013 assembly elections by splitting its votes through the Karnataka Janata Party (KJP), Yeddyurappa is contesting for the first time in a Lok Sabha battle from his home turf Shimoga.
He has been fielded in place of his younger son and sitting member B.Y. Raghavendra.
It is a litmus test for the BJP to retain the seat. Yeddyurappa is locked in a triangular fight with JD-S' Geetha, wife of Kannada cine star Shivarajkumar and daughter of former chief minister S. Bangarappa, while a resurgent Congress has put up Manjunath Bhandary.
As Lingayats, the dominant community in the state with 18 percent of vote share, are willing to back its leader Yeddyurappa, the BJP is upbeat on holding on to Shimoga as people in the Malnad region benefited a lot during its five-year rule in the state.
Yeddyurappa had to resign July 31, 2011, following his indictment by the ombudsman (Lokayuktha) in a mining scam.
Geetha is considered an outsider as she has lived in Bangalore over the past two decades though her father (Bangarappa) hailed from Sorab town in the constituency and belongs to an equally powerful Idiga community.
The BJP says their constituency will benefit if Yeddyaurappa is elected as he could become a cabinet minister in the event the NDA returns to power.
Deve Gowda, Moily and Singh have not changed their constituencies while Sadananada is trying his luck from Bangalore North and Kumaraswamy from Chikkaballapur, about 70 km from here.
Moily, who hails from Dakshina Kannada in the coastal belt, shifted to Chikkaballapur in the 2009 elections.
The fledgling Aam Aadmi Party (AAP) has also fielded candidates in all the 28 constituencies and has vowed to defeat Moily, Yeddyurappa and Kumaraswamy whom it categorised as "most corrupt" along with Ananth Kumar and B.R. Sriramulu of the BJP.