While Azad, Leader of Opposition in the Rajya Sabha, has been made in charge of Uttar Pradesh (UP), Nath will look after Punjab and Haryana, party General Secretary Janaradan Dwivedi said.
Assembly elections in Uttar Pradesh and Punjab are scheduled early next year.
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Appointments are being seen as a precursor to further restructuring of the All India Congress Committee Secretariat (AICC).
The reshuffle came at a time when talk of Rahul Gandhi being elevated as the party chief had again gained ground.
Sonia Gandhi made the changes a day after the biennial elections to the Rajya Sabha. During elections party witnessed cross voting by some party legislators in Uttar Pradesh and alleged deliberate faulty marking by its 14 legislators in Haryana which led to their votes being declared invalid and resulted in the defeat of Congress backed candidate R K Anand. There were allegations of internal sabotage at the behest of the former Haryana chief minister Bhupinder Singh Hooda.
Azad, 67, is a Gandhi family loyalist and a former Chief Minister of Jammu and Kashmir, while 69-year-old Nath is the most senior member of parliament in the current Lok Sabha having won from his pocket borough of Chhindwara nine times.
Azad was the AICC general secretary in charge of UP couple of times before. Nath was a General Secretary in charge of key states like Gujarat and West Bengal earlier.
His name was doing rounds as the possible new party chief in Madhya Pradesh.
Congress has roped in poll strategist Prashant Kishor, who successfully managed Prime Minister Narendra Modi's Lok Sabha campaign in 2014 and Bihar Chief Minister Nitish Kumar's in 2015, to aid and assist the party's UP and Haryana units.
In UP, Congress had secured just two seats in the last Lok Sabha elections with Sonia Gandhi and Rahul Gandhi emerging victorious from their traditional seats of Rae Bareli and Amethi.
The Congress is in political wilderness in UP since 1989 following emergence of divisive Mandal-Mandir politics and rise of the Bahujan Samaj Party, which took away its crucial dalit vote base.
In Punjab, Congress is in the opposition for the last nine years and is making a determined bid to capture power from Shiromani Akali Dal-Bharatiya Janata Party combine at a time when Aam Aadmi Party has also come up as a serious contender for power.
The appointment of seasoned politicians like Azad and Nath came amid calls for a major surgery within the party following its recent debacle in assembly polls in four states, including Assam and Kerala.