<Tr> <Td> Indian National Congress (Urs) </Td> <Td> 10,449,859 </Td> <Td> 5.28 </Td> <Td> 13 </Td> <Td> New </Td> </Tr> <Tr> <Td> Communist Party of India </Td> <Td> 4,927,342 </Td> <Td> 2.49 </Td> <Td> 10 </Td> <Td> + 3 </Td> </Tr> <Tr> <Td> All India Anna Dravida Munnetra Kazhagam </Td> <Td> 4,674,064 </Td> <Td> 2.36 </Td> <Td> </Td> <Td>--16 </Td> </Tr> <Tr> <Td> Dravida Munnetra Kazhagam </Td> <Td> 4,236,537 </Td> <Td> 2.14 </Td> <Td> 16 </Td> <Td> + 14 </Td> </Tr>

What were the reason which led to the midterm election in 1980