"Therefore, Chandy Oommen will win by a huge margin," he said.
Hours after the Election Commission declared September 5 as the date for the bypoll to Puthuppally assembly constituency in Kottayam district, the Congress announced that Chandy Oommen -- son of late Oommen Chandy -- would be their candidate for the seat left vacant by the death of the former chief minister.
The AICC in a statement said that Congress chief Mallikarjun Kharge has approved the candidature of Chandy Oommen as the party candidate for the byelection to Puthuppally constituency.
Mr Chandy died in Bengaluru on July 18.
Kerala Pradesh Congress Committee (KPCC) president and MP K Sudhakaran, informing the media in Delhi that AICC has given the green light to field Mr Oommen as the UDF and party candidate, said, "He will begin campaigning from tomorrow. KPCC will form a team which will be responsible for the campaigning work."
Mr Sudhakaran also said that the Puthuppally bypoll would be the beginning of the "politics of love" proposed and encouraged by Congress leader Rahul Gandhi.
"Chandy's memories would be there in Kerala's political arena, during the bypolls as well, in the people's minds. His memories will sway the people's minds, Congress is confident of that.
"Therefore, Chandy Oommen will win by a huge margin," he said.
Mr Sudhakaran also said that the bypoll would be an assessment of the ruling LDF government in the state.
After the announcement, Chandy Oommen told reporters that it was a big responsibility that has been given to him by the party.
"I will carry out the responsibilities given to me to the best of my abilities. My father represented the constituency for 53 years and it would be a challenge to perform in that same position.
"So it is a big challenge given to me by the party," he said.
He also conveyed his respect and gratitude to the top leadership of the party at the national and state levels.
Mr Oommen also said that since the bypoll was being held after his father's death, that would be on the people's mind, but at the same time it would also be a political fight.
He also offered prayers at his father's grave in St George Church at Puthuppally.
With his selection as the bypoll candidate, the recent speculations that he would be replacing his father have come true.
Even his sister Maria Oommen, earlier in the day, said that if the party wants someone from the family, it will be her brother Chandy Oommen.
Other Congress leaders, including Leader of Opposition in the state assembly V D Satheesan, Ramesh Chennithala and Thiruvanchoor Radhakrishnan, spoke along similar lines as the KPCC chief.
Mr Satheesan said that the UDF was confident of achieving a resounding win with a margin which would be greater than that of the last time when Mr Chandy won with a margin of close to 10,000 votes.
He said that byelection-related preparations have already begun in Puthuppally, a Congress stronghold for 53 years thanks to Mr Chandy, and the bypoll would be a trial of the government in the people's court.
Mr Chennithala said the campaign strategy would focus on the contributions of Mr Chandy during his decades-long political career and the "poor administration" of the ruling Left government.
Radhakrishnan said the party will face the byelection politically.
As the Congress struck a confident pose, the ruling Left front too appeared hopeful of success in the bypoll.
CPI(M) state secretary M V Govindan said bypoll preparations have already begun and the Left front would soon decide upon a candidate after holding discussions with all its allies.
The Left front's bypoll campaign would be focused on depicting the Congress and UDF as anti-development just like the BJP, he said.
He rejected the notion that public sympathy might be in favour of the Congress, saying that the bypoll would be contested politically.
Mr Govindan was also unperturbed by the Congress's contention that the bypoll would be an assessment of the ruling Left front.
"Let it be an assessment," he said.
State Tourism Minister P A Mohamed Riyas said that the political situation in the state was in favour of the LDF.
The counting of votes for the September 5 bypoll will be held on September 8.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)