His remarks come in the wake of the AAP suffering a massive bruising in the by-poll for the Rajouri Garden assembly seat, which was won decisively by the BJP.
"Autowallahs, rickshaw-wallahs, Rehri-patriwallahs (auto-drivers and rickshaw and street cart pullers) to people living in unauthorised colonies, they all voted their heart out in the 2015 Delhi Assembly elections. But did Arvind Kejriwal's party do anything for them after assuming power?"
People from Bihar and Uttar Pradesh, living in Delhi, now feel cheated and are disillusioned with the AAP, he held.
"After seeing and hearing about Nitishji's governance in Bihar, they are warming up to the JD(U) as an electoral alternative," Mr Jha told PTI in an interview.
Purvanchalis, according to Mr Jha, constitute about 30 per cent of the electorate in the national capital and the JD(U) is going all-out to woo this "kingmaker community".
The party is holding a series of meetings in areas such as Uttam Nagar, Burari, Laxmi Nagar and Mayur Vihar, which are heavily populated by migrants from Bihar.
Bihar Chief Minister Nitish Kumar held two back-to-back rallies and a roadshow in the capital earlier this month. On Monday, the JD(U) released a video message of the party chief. In the message, Mr Kumar again pitched for full statehood status for Delhi, while seeking support for the party's candidates fighting the civic polls. He held up Bihar's prohibition and good governance model, the poll plank JD(U) is riding on.
"We are a regional party with a national leader, who enjoys a clean and incorruptible image. People in Delhi have known him since his Railway Ministry days and we are confident that his charisma will work in our favour in Delhi, even though we have barely started here," Mr Jha said.
The party's national general secretary also hit out at Mr Kejriwal over his promise to waive house taxes if it came to power.
"A house tax waiver will benefit whom? Will it benefit the poor and middle-class people living in Burari or Sangam Vihar in unauthorised colonies, which do not come under the ambit of the tax or will it benefit upper class people living in areas like Vasant Kunj and Civi Lines," he asked.
"He (Arvind Kejriwal) promised the moon before the Delhi polls and now (this is) another stunt. His party will lose out big time in the MCD polls. And this is not my hunch but we are seeing it at the ground level," he said.
Besides, he added, Purvanchalis had an "emotional connect" with the JD(U).
The AAP has not left any stone unturned to woo the community, campaigning aggressively in areas dominated by the community. Along with other party leaders from Bihar and Uttar Pradesh, Mr Kejriwal has been holding rallies.
The JD (U) had fielded 111 candidates for the polls, but 13 candidates' nominations were cancelled.
The party is also wooing other communities such as Muslims and Sikhs. Former national Taekwondo champion Razia Bano has been fielded from Okhla, while four Sikh candidates are in the fray in Tilak Nagar, Rajouri Garden and two other wards.
"The 350th anniversary of Guru Gobind Singh in Patna haswon the hearts of Sikhs world over, so we are wooing them also," he said.
Mr Jha held that in 60 or 70 of the 98 wards, the party was going to give "a tough fight". The wards include Badarpur, Burari, Kirari, Madanpur Khadar, Vinod Nagar and Patparganj, he said, claiming that nearly "a thousand supporters from the AAP", including some senior leaders, had joined the JD(U) in the last few months.
He also attacked the Bharatiya Janata Party (BJP), which rules the Muncipal Corporation, for "leaving the city in a garbage mess".
"They (BJP) have decided to field only fresh faces. How convenient. What about the report cards of the 150 councillors of the last ten years," he asked.
The BJP has been ruling the MCD since 2007. Delhi has 272 wards.