"The reality is that the political support of the Congress has dramatically slipped and the BJP has never been a national party," one senior Janata Dal (United) source told The Telegraph.
"Therefore if the numbers are viable enough to keep Narendra Modi out, as they should be, the Congress will have the opportunity of joining a third or alternative front to keep Modi out," he added.
Since the split in the Congress Party ranks under Indira Gandhi in the late 1960s, power for either secular Congress or extremist BJP was defined by ability to strike alliances with local state-based parties.
In 2014 elections, BJP prime ministerial candidate Narendra Modi was able to strike an alliance under the title of National Democratic Alliance (NDA).
The alliance, which includes the Punjab-based Sikh party, the Shiromani Akali Dal, the Tamil Nadu-based MDMK and the Bihar-focused Lok Janshakti Party of Dalit leader Ram Vilas Paswan, needs to win 272 seats in next parliamentary elections.
Yet, recent opinion polls said that the NDA may win around 200 seats. Another poll by the television news channel NDTV suggested it could win as many as 229, with the BJP itself winning 195.
Studying different scenarios for next elections, politicians said that if Congress and BJP failed to secure enough number of seats a third front would appear, gathering the non-Congress, non-BJP parties.
"If the BJP and NDA get under 200 seats it will be difficult for them to form a government because it is difficult under Modi for others to ally with them – all of the possible allies have people of many faiths in their own areas of influence. Mr Modi is anathema to Muslims," the senior Janata Dal (United) source said.
The so-called Third Front of regional parties would include the Samajwadi Party, Communist Party of India (Marxist), Janata Dal (United), and the AIADMK which rules in Tamil Nadu.
This front would form group with other secular, regional parties to form a winning alliance with the Congress Party's United Progressive Alliance.
Shaheed Siddiqui, a former MP from Uttar Pradesh and a leading Muslim voice in India, said he doubted whether the regional parties necessary to form a Third Front government could overcome their local rivalries.
Siddiqui asserted that Mamata Bannerjee and the Communists are bitter rivals in West Bengal, Dalit leader Mayawati and Mulayam Singh Yadav's socialist Samajwadi Party are enemies in Uttar Pradesh.
Jayalalithaa's AIADMK will not work with the DMK in Tamil Nadu, he added.
For Congress supporters, the secular party remained as the only party capable of leading a political alliance to the government headquarters.