Liberal Democrat leader Charles Kennedy's stroll around a map of Britain in his party's first election broadcast has proved a ratings winner.
His advert, broadcast across the five terrestrial channels at different times on Wednesday, pulled in 13.2m viewers.
The Tories' advert shown on Tuesday attracted a total audience of 12.8m.
Labour's broadcast, showing Tony Blair and Gordon Brown discussing how they reformed the party together, drew in a viewing audience of 11.9m on Monday.
In the Lib Dem ad, Mr Kennedy is seen wandering around a virtual map of Britain.
His constitutional is interspersed by clips of voters explaining how they have been let down by Labour and Tony Blair.
The ad attracted an audience of 9.7m, or 53.5% of the number of people watching TV at the time, when it was simulcast on BBC1 and ITV1 at 1845 BST on Wednesday.
Some 4.3m, or 23.7% of the available audience, watched it on BBC1 between the news and Smart Spenders, while 5.4m, or 29.8%, watched it on ITV1 before the soap Emmerdale.
On BBC2, 1.7m, or 11.4% of the total audience, watched the ad at 1745 BST after the Weakest Link.
On Channel 5 at 1915 BST, 200,000 people, or 0.9% of the available audience, tuned in to the broadcast.
Meanwhile 1.6m, or 7.4%, saw the broadcast on Channel 4 at 1945 BST ahead of the show Relocation, Relocation.
The Conservative broadcast focused on Michael Howard's leadership.
Labour's four-minute advert, featuring Mr Blair and Mr Brown, was produced by Oscar-winning film director Anthony Minghella, whose credits include The English Patient and Truly, Madly Deeply.