Hyderabad: The battle-lines are now drawn for political parties with the Election Commission today announcing the schedule for by-elections to 18 Assembly and one Lok Sabha seat in Andhra Pradesh.

The bypolls in 16 of the 18 seats are necessitated due to disqualification of sitting Congress MLAs who switched loyalty to Kadapa MP Y S Jagan Mohan Reddy and voted against the Congress government during a floor test in December last.

Another MLA quit in support of Jagan while actor-turned-politician Chiranjeevi resigned as MLA following his election to Rajya Sabha.

The by-election has been necessitated for Nellore Lok Sabha constituency as the sitting Congress MP quit in support of Jagan.

Of the 18 Assembly segments, only one (Parkal) is in Telangana and all others are in coastal Andhra and Rayalaseema regions. The Nellore Lok Sabha seat is in coastal Andhra.

The bypolls are important for Jagan and his fledgling YSR Congress as a poor performance would derail his political journey ahead of the Lok Sabha elections in 2014.

For ruling Congress too, the bypolls are significant as success is a must to retain power in 2014 assembly elections.

Having drawn a blank in the bypolls held last month for seven Assembly seats, it faces the twin challenge from Jagan and main Opposition TDP.

TDP had also failed to win a single seat in the March bypolls. The Chandrababu Naidu-led party must put up a sound performance in the bypolls to remain a major political force in state politics, observers said.