For a debate that covered such worthy topics as interest rates, taxation, industrial relations and the response to global warming, the longer-term impact of Sunday night on the election campaign seems to lie with utterly trivial matters that have taken on a heavy symbolism.

The worm debate is still going in today’s Australian. Ray Martin hasn’t been this angry since he found John Safran going through his garbage. Noted pugilist Glenn Milne has come out swinging in reply. At this rate, the worm will get its own spin-off show.

And amidst all the acrimony and bad puns, the Liberals have managed to paint themselves as the enemies of free speech, if not by pulling the plug on Nine’s feed, then by insisting on a worm-free debate in the first place. As a consequence, not merely did they lose the fight on Sunday night, they’ve lost the fight over the fight.

Peter Costello, sensibly, has declared he doesn’t care if his debate with Wayne Swan is wormed. Unfortunately, interest rate rise or not, viewers won’t exactly be queuing up to watch that mighty clash.

But that Prime Ministerial twitch has now also broken out from the debate and taken on a life of its own. Howard has always been prone to nervous twitches – he produced a ripper during the 1996 debate with Keating that looked like an extended Jimmy Cagney impersonation. But, thanks to YouTube, Sunday’s effort has been spread far and wide, and it is almost impossible not to watch it over and over again. No wonder both The Chaser and Shaun Micallef played it ad nauseum last night.

Throw in last week’s interest rates gaffe and his slip yesterday about funding defence colleges until 1916 (perhaps this time we can win at Gallipoli?), and Howard is now becoming a figure of general ridicule. This is Billy McMahon country, from whose bourn no politician returns.

Toward the end, Paul Keating, with his hoots of “get a job!”, became a figure to be despised rather than listened to. Andrew Peacock never survived Keating’s incessant mockery and became a walking cliché. Gough Whitlam, too, with his bombast and “men and women of Australia” shtick, turned into a self-parody before leading Labor to defeat in 1977.

Howard now appears to be suffering the same fate. He has always had to endure the mockery of comics, leftwingers and latte-sipping ‘litists, particularly during his first, dire go as Liberal leader in the 1980s. But there was always a basic, if grudging, respect among voters for his doggedness, and it was rewarded in 1996. That respect is now ebbing away fast. Like it or not, Howard is starting to look old and silly.

Liberals should pray for Prime Ministerial surefootedness between now and election day. One trip on that morning powerwalk and it will all be over.