An average audience of 4m people tuned in to watch Thursday night's prime ministerial debate on Sky, according to early overnight figures.
Ratings for the showdown were well down on last week's ITV1 debate, which attracted an average 9.4m viewers.
The debate was screened live on a variety of outlets, including the BBC News Channel, the BBC HD channel and a later repeat on BBC Two.
The third and final debate is scheduled for next Thursday on BBC One.
The programme's average audience share was 8.7%.
The majority of people tuned in to Sky News to watch the debate between Prime Minister Gordon Brown, Conservative leader David Cameron and Lib Dem leader Nick Clegg, with 2.1 million watching.
The total audience on Sky News peaked between 2100 BST and 2115 BST when 4.5 million people tuned in.
The debate was also broadcast on Sky 3, which was watched by 586,000 viewers.
Some 1.3 million people watched proceedings live on the BBC News Channel, while an average of of 300,000 viewed the 2330 BST repeat on BBC Two.
Last week Mr Clegg's performance during the programme was praised and he was hailed the winner.
Opinion polls taken immediately after the second debate gave conflicting verdicts over whether Mr Cameron or Mr Clegg came out on top but they agreed that the margins between all three contenders were much tighter than in the first debate.
But BBC polling expert David Cowling said there had been a significant drop in the number of people who thought Mr Clegg had won, with Mr Brown having the most improved ratings.
All three leaders clashed over global affairs, including Europe, climate change, tax, nuclear weapons and sleaze.