It was the Ed, Vince and Alan show at this morning's Yes2AV event. Miliband and Cable were joined by a "special guest", Alan Johnson, who looked notably more relaxed than he did as shadow chancellor.
Johnson, one of Labour's most committed electoral reformers, made some of the most persuasive and original arguments we've heard against first-past-the-post. He pointed out that no young democracy (South Africa, the former eastern bloc, former Latin American dictatorships) had chosen to adopt the system.
He also remarked that David Cameron was content to put his name to a bill that will lead to the election of police commissioners using the Supplementary Vote, a variant of AV.
"I believe first-past-the-post should be left where it belongs on the race track," he concluded.
Vince Cable picked up the theme of hypocrisy, mischievously observing that if the Conservative Party had used FPTP for its leadership elections, "I would now be conducting my amicable, coalition-like discussions on immigration with David Davis." Elsewhere, he noted that Boris Johnson, a "vehement opponent" of the Alternative Vote, had not complained about the use of the Supplementary Vote in the London mayoral elections. The message of the No campaign is "do as we say, not as we do", he concluded.
Cable also found time to ridicule the suggestion that AV is some kind of "alien import", pointing out that it is commonly used throughout Britain by charities, businesses, trade unions and political parties. And he rejected the "bizzare" claim that AV will benefit the BNP (Nick Griffin's party even opposes the system), acidly noting that "the people who run the BNP may not be very bright, but at least they've worked out what's in their self-interest".
But while Johnson and Cable mounted an effective rebuttal operation, we heard little about the merits of AV itself. As I've noted before, one of the biggest problems  for the Yes campaign is that many of its own supporters aren't keen on the system. Johnson, for instance, has previously confessed: "I'll support AV, but my heart won't be in it in the same way as if it was the proper thing."
As long-term supporters of proportional representation, Johnson and Cable are far happier making the case against first-past-the-post than they are making the case for AV.