"There were some problems between the allies because they could not campaign unitedly. Even other opposition parties were unable show their unity as well," she told reporters here.
As per initial trends, the ruling AIADMK in Tamil Nadu has garnered substantial votes, pushing arch rival DMK to the second place in the by-polls. The BJP is likely to suffer a defeat in Srirangam.
While NDA's key ally PMK kept away from the elections, top leaders of another ally DMDK did not campaign during the run up to the by-polls.
"I think the by-poll results should make the allies understand that we will not be able to achieve the goal in 2016, if we are not united," she underlined.
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Alleging that Dravidian parties bribed voters in Srirangam elections, she charged that, "Money distribution and muscle power was in full swing in the by-elections, hampering voters to think independently."
Soundararajan also charged that a section of election officers favour ruling parties whenever by-elections are held in the State.