Bitter rivals Aam Aadmi Party and the Congress are understood to have been in touch to explore the possibility of an electoral alliance for the seven Lok Sabha seats in the national capital.

AAP sources said back-channel talks are currently on between the two parties. However, there is no official word on the alliance between them.

The buzz got traction after AAP for the first time took part in an Opposition meeting last week, which was attended by the Congress.

From the Aam Aadmi Party's side, talks are being held by a senior party leader and member of the AAP's apex decision-making body, the Parliamentary Affairs Committee, the sources said.

Interestingly, the AAP and the Congress have been at loggerheads in Delhi and Punjab. Until August, Delhi chief minister Arvind Kejriwal had said that voting for the Congress was akin to voting for the BJP.

The AAP had boycotted the poll for electing the deputy chairman to the Rajya Sabha in August, stating that it was upset over the Congress not asking for its support for the joint Opposition candidate fielded by it.

The bone of contention is believed to have been the number of ]seats the Congress wants to contest in Delhi. Of the seven seats in Delhi, the AAP is not ready to cede more than two to the Congress, the sources said.

Of the seven seats, the AAP has announced constituency in-charges for six. These in-charges will eventually be declared the candidates. This means, the AAP has to ask one or two of its candidates, who have already started campaigning, to withdraw from the fray.

Interestingly, the local leadership of the Congress is not keen on tying up with the AAP, but the top brass is understood to not have been averse to the idea.

The AAP and the Congress have more or less the same voter base in the national capital.

Since the 2013 Assembly polls in Delhi, the vote share of the AAP and the Congress had oscillated, but the BJP's vote percentage remained the same.

In 2013, the BJP bagged 31 seats and secured 33.07 per cent of the vote share while the Congress got 24.55 per cent with eight seats. The AAP, in its debut performance got 29.49 per cent of votes and bagged 28 seats.

In the 2014 Lok Sabha polls, the BJP swept the elections scoring 7-0. The AAP came second while the Congress stood third in vote share. However, in six seats, the votes of the AAP and the Congress combined were much more than that of the BJP.

In 2015, the AAP registered a stupendous victory, winning 67 seats and 54.34 per cent vote share while the Congress drew a blank and got only 9.65 per cent of the vote share. However, the BJP's vote share remained more or less the same to 32.09 per cent, despite the drubbing.

In the April 2017 Rajouri Garden bypoll, though the BJP wrested the seat from the AAP, the Congress came second and the AAP candidate lost his deposit.

In the 2017 MCD polls in June, the Congress's vote share rose sharply to 21.28 percent, while the AAP bagged around 26 per cent, less than half of what it got in 2015 Assembly polls.