Weight of Establishment stepping up In campaign
For the chancellor, the prime minister and the Remain campaign, this is the week they hope undecided voters begin listening.
For starters, 200 pages of hypothetical number crunching has emerged that boils down to one core message: if you vote to leave the EU your wallet will suffer, George Osborne asserts.
The country wouldn't just be harmed in the possible immediate chaos of a vote to leave, but the Treasury claims the economy would significantly, and irrevocably, shrink.
The Leave campaign rejects the official analysis - saying the Treasury has been wrong before. They say leaving the EU will ultimately make the country richer.
But it is becoming harder by the day for those arguing for exit not to offer clear-costed alternatives. And there won't be much let up for them.
On Thursday the most powerful man in the Western world arrives in the UK - and US President Obama is expected to make plain his support for us remaining in the union.
Yet this campaign, like any other, is a credibility contest too.
The Treasury's economic warnings will only swing undecided voters if they are willing to listen. President Obama's intervention might irritate as well as inspire.
But the weight of the Establishment is moving more and more openly in favour of Remain, leaving the many politicians arguing for exit seem like rebels with a cause.