Thiruvananthapuram: If one surprise sprung by Sunday's Vengara Assembly by-election results is the Indian Union Muslim League's reduced victory margin, the other is the BJP losing its traditional third spot to a Right-wing Muslim party.

League ally Congress was quick to link the two developments, alleging a "secret alliance" between runner-up CPM, which has increased its tally, and the BJP.

"The BJP and the CPM had a secret alliance this election, which explains where the BJP votes went," senior Congress politician V.M. Sudheeran claimed.

A few analysts, however, suggested that some disillusioned young League supporters may have voted for the Social Democratic Party of India (SDPI), the political wing of the Popular Front of India, which finished third ahead of the BJP.

A crowing CPM attributed its improved showing in the seat, which falls in the League stronghold of Malappuram in north Kerala, to "the increased acceptance of our party and our government's policies".

Party state secretary Kodiyeri Balakrishnan further alleged an "organisational collapse" in the Congress-led United Democratic Front, where the League is a partner.

The BJP was in shock at the setback, which comes amid its high-voltage Janaraksha Yatra across the state to protest alleged Left violence against Sangh-BJP cadres.

The party had claimed that the march, flagged off by party president Amit Shah and attended by Uttar Pradesh chief minister Yogi Adityanath, would change Kerala's political landscape.

League candidate K.N.A. Khader has defeated the CPM's P.P. Basheer by 23,310 votes, which is 14,747 less than the margin by which the League's P.K. Kunhalikutty, now a Lok Sabha member, won the seat during the 2016 Assembly election.

Vengara had elected Kunhalikutty with a margin of 38,237 votes in 2011 and 38,057 votes last year. When Kunhalikutty contested the Malappuram Lok Sabha seat, which fell vacant after the death of E. Ahamed, in April this year, he led by more than 40,000 votes from the Vengara segment. He was elected by a margin of 171,023 votes.

The BJP, which had polled 7,055 votes in 2016, garnered only 5,728 this time. Its candidate K. Janachandran finished fourth behind K.C. Naseer of the SDPI, who polled 8,648 votes - nearly thrice the 3,049 votes the party had secured last year.

The BJP tally is lower than the 5,952 the party had polled from the Vengara segment during the April Lok Sabha by-election.

Its then candidate, N. Sreeprakash, had promised good quality beef if elected to try and offset any backlash against the party's cow policy.