By Nick Assinder
Political Correspondent, BBC News website
It has been said before. But could this be the point at which power finally transferred from Tony Blair to Gordon Brown?
A coincidence of events has seen Gordon Brown's political stock rising at the exact time that Tony Blair's is falling.
Brown's stock is rising
It is not just the chancellor's deliberately prime ministerial budget statement, or Mr Blair's involvement in the "cash-for-peerages" row that has sparked this atmosphere in Westminster.
There is a growing feeling amongst many MPs of all parties that the "orderly transition" of power, whether planned between the two men or not, is far more advanced than perhaps they had originally suspected.
There is a widespread belief that this autumn's Labour Party conference will be Tony Blair's last as prime minister.
At the same time many believe Mr Brown has just delivered his last Budget. They claim it would be difficult , if not downright embarrassing, for him to have to deliver a repeat premier-in-waiting performance in a year's time.
Certainly, Mr Brown's Budget has been almost universally interpreted as his manifesto for power. Even those who criticise the content of the package have seen it as such.
The House of Lords in full colour for the last Queen's Speech - was it Blair's last?
Meanwhile, Mr Blair has found himself embroiled in the row over Tessa Jowell's husband David Mills' links with Italian premier Silvio Berlusconi and, more dangerous, the cash-for-peerages row.
Neither of those affairs have so far proved fatal, but equally there are no signs they have gone away for good. And they have certainly weakened Tony Blair's standing.
Mr Blair did get his controversial education bill through - but it only came thanks to Tory votes, leading to questions over whether he has now got the only reform he is likely to get.
It is being argued that, now he has got his way on education, he should quit while he is (sort of) ahead.
The next scheduled tests are the looming local elections, just a couple of months away, which are inevitably being seen as an opportunity for voters to deliver their verdict on the government.
On this occasion the result will immediately be interpreted as a verdict on Tony Blair and whether he has become a liability rather than an asset.
Brown is looking towards No 10
Perhaps more importantly, there is a feeling amongst many on the Labour benches that what is needed to recover from the recent setbacks - specifically the taint of sleaze - is a fresh start.
The prime minister's supporters, of course, claim we have been here many times before and Mr Blair has kept his nerve and continued with the job in hand.
They stress that nothing improper has been proved against him and that he is personally as committed to, and energetic about, his third-term programme as ever.
And they argue that the current speculation is being whipped up by the usual backbench suspects, the media and opportunistic opposition parties.
None the less, there is now a growing list of Labour-supporting media, led by the Guardian and the New Statesman, backbench MPs and, it is whispered, ministers who have decided it's time for a change.
Add that to the generally fevered atmosphere in Westminster and it is hard to escape the feeling that those famous tectonic plates are indeed moving.