Cameron has grasped the nettle and found a golden bullet to get to grips with the expenses scandal, leaving Billy-no-mates Brown high and dry.
Looking genuinely angry as the Tory toffs side of the scandal blew up in his face, the prime minister-in-waiting did more than a little before it was too late.
As the government-in-waiting and the Tories in the Telegraph firing line, today was always about how Cameron would deal with the squalid scandals among his own kind.
Dave didn't disappoint. He said sorry, again. He ordered his motley crew of MPs to repay questionable allowances, promised future transparency, stopped the rot of future extravagant claims and made a start on the flipping second homes fiddle at the heart of the scandal.
It was an impressive performance but for voters maybe just that - a performance. The jury is still out on whether he's done enough to capture and keep the political high ground before the elections swing around.
The race was on to find a golden 'expenses' bullet to clear the air, make peace with voters and come out with a scrap of dignity.
But where was Brown? Delivering a speech on 'crime', while Mandy had a go at 'enterprise'. How fitting.
Both Brown and Cameron have been sent scrabbling around for the magic bullet to get themselves out of the mess without shooting themselves in the foot.
The rot cannot be left to fester away dragging down with it any dignity left in parliament. But that calls for firm, bold, trusting leadership.
Battered Brown's political cabinet looked grim-faced today as they tried to salvage something from the wreckage of the expenses scandal and his doomed premiership.
Brutal Brown's petty style of politics, looking for someone to blame and a sacrificial lamb for the slaughter are useless political tools for the crisis which has engulfed the whole of Westminster.
The Labour Party has to find a way to break free from the stranglehold of sleaze and scandals, with or without Brown.
The answer from Cameron was to tell his greedy lot in the most blatant cases to pay back their ill-gotten gains or clear off with their tails between their legs. As Benedict Brogan observes, Cameron looked every inch a leader and Brown's lot don't like it one bit.
Cameron has faced the music head on, Brown left his cheerleader Hattie Harman to play catch-up and do the dirty work. But trying to get any kind of reform past New Labour's gatekeeper would be impossible while speaker Martin remained in office.
No change there. Though there are signs of a start to rid the commons of the excuse for a speaker who's turned into a national disgrace.
The weekend of spinning and bleating about only obeying orders and "following the rules", blaming it on "the system" are well and truly over and cut no ice in the court of public opinion.
Brown’s disastrous premiership is over. But he still needs to find a golden 'expenses' bullet and fire a final shot for the sake of his Party.
Taste the difference. Brown was interviewed on a train when the Telegraph story broke – doing everything he can, getting on with the job, blaming "the system" all with smug self-satisfied arrogance.
Echoing the public’s anger, Cameron showed again his sensitive side. Sensitive to the mood of voters and the ballot box, sure but chiming with voters who are pissed off with the whole sordid expenses scandal. Compare that to Brown's moronic performance.
Some top Tories who've been caught out have been busy writing pay-back cheques this afternoon, and so they should. Cameron named and shamed and told them bluntly where to stick their squalid expenses, at a stroke striking the right balance.
As for Brown, that golden bullet has got his name on it. In times of public disgust first impressions count. It boils down to trust.
Many voters are unsure whether they can trust Cameron. But Brown? His past record speaks for itself. They wouldn't trust him as far as they could throw him.