Former South Australian premier Mike Rann is a prolific tweeter. When he was premier he used the social media platform to praise his buddy Lance Armstrong — the seven-time Tour de France winner used to call him “Ranny” — for his government-funded attendance at the Tour Down Under cycling race and his support for cancer research in Adelaide.

Yesterday he tweeted about his encounter with an 80-year-old crocodile and his upcoming holiday to Sydney. But not Armstrong. Not over the last few days, as the world learned — definitively for the first time — the cycling hero was nothing but a fraud.

A former friend of Armstrong, who witnessed a private hospital confession over systematic doping, told the ABC: “This is the biggest fraud in the history of sport, the biggest.”

Was Rann complicit? Was the government, which signed large cheques to Armstrong for his appearance in three cycling events? Is Adelaide’s Flinders Centre, which took his foundation’s cash to study cancer? No. They’re guilty of what all fair-minded sports fans fall victim to: presuming innocence until proven otherwise.

The latest evidence from the US Anti-Doping Agency appears unequivocal. Armstrong is a cheat. We’ve all been had, even “Ranny”.

That’s embarrassing, certainly. And it demonstrates why politicians should be wary of hitching their wagons to celebrities who could stray. The Victorian government wouldn’t have paid Tiger Woods the extraordinary sum of $1.5 million in 2010 to appear at the Australian Masters had it known about his off-course indiscretions.

But Armstrong certainly raised cash, for South Australia and medical research, however rubbery the figures may be. To condemn those who didn’t react to rumours of cheating would mark a sad day for professional sport.