In contrast, the Congress vote share declined 9.26 per cent to 31.89 per cent in five years from 41.15 per cent in 2014.
The Janata Dal-Secular (JD-S) vote share, however, declined marginally 1.4 per cent in five years to 9.68 per cent from 11.07 in 2014.
Both the ruling allies won only one seat each though they jointly contested in all the 28 seats, with the Congress in 21 and JD-S in 7 under a pre-poll seat-arrangement to prevent their votes from being divided and favouring the BJP.
An independent - multi-lingual south Indian actor Sumalatha Ambareesh, supported by the BJP, won in Mandya, which recorded the highest voter turnout at 80.24 per cent in the state in the first phase of polling on April 18.
Of the total 13,72,308 votes polled, Sumalatha secured 7,03,660 while her rival Nikhil Kumaraswamy of the JD-S got 5,77,784 and she won by a margin of 1,25,876 with the remaining 90,864 shared by other candidates, including other independents.
The ruling allies' hopes of benefitting from their combined 'secular' votes by fielding common candidates in all the seats were dashed as their combined vote share of 41.57 per cent was 9.78 per cent less than the BJP's 51.35 per cent.
In contrast, the combined vote share of the Congress and JD-S in the 2014 general election - 52.22 per cent was more than BJP's 43.37 per cent.
"Though the allies fielded common candidates, non-division of their votes did not benefit them, as there was no transfer of votes between them, as evident from the number of votes polled and the margin of defeat or victory of their contestants," a poll analyst told IANS.
In the 2014 election, the BJP won 17, Congress 9 and JD-S won two seats in a triangular contest as the allies fought against each other as they had done since the 1999 mid-term Lok Sabha polls.
The Congress vote share increased to 41.15 per cent in 2014 from 37.65 per cent in 2009. In contrast, the JD-S vote share declined to 11.07 per cent in 2014 from 13.57 per cent in 2009.