What a tonic Jeremy Corbyn has been to the Labour leadership campaign with his particular heresy of radical ideas and anti-establishment energy.
It is like shaking hands with the 1970s. How invigorating also for us bystanders after nearly 20 years of politics meeting in that sterile no-man's land the centre ground.
Nobody expected to put together 'Prime Minister Jeremy Corbyn' in one sentence until a few weeks ago, and now they dare.
As the musician and artist Brian Eno rightly asks in a very measured newspaper article, which was inspired by how 'electrifying' his 25-year-old daughter found a Corbyn rally: 'Why not?'
Despite many voices in the media, both to left and right of the spectrum, determined to keep Jeremy Corbyn and Downing Street apart; they obviously are fitting together for some.
Let's face it: his arrival has ignited an otherwise predictable, measured leadership contest between three other people who actually seem like just one other person. They all even went to Oxford or Cambridge.
Corbyn (North London Polytechnic) has enjoyed an ascendancy, despite the legions ranged against him and the critical attention focussed on his vest and sandal wearing, because he is exciting voters.
We should be grateful, regardless of the politics involved, that he is there. He actually seems a catalyst for ideas, a reminder of an absent part of the Labour face for decades.
Corbyn is forcing us to dust off those positions on everything from selective education to the future of the monarchy; the merits of vegetarianism and nuclear disarmament. Did the banks get off lightly? And yes, it was a hell of a lot of our money that bailed them out, since he mentions it.
The appeal could just be vicarious, of course. We have five years of Conservative government ahead. The prospect of Conservative-lite opposition, too, is a deadening one.
But it will also not do the Conservatives much good if they face a 'mini-me' Labour Party determined to make its own big ideas small.
The Labour leadership candidates could scarcely seem more timid and unchallenging of Conservative orthodoxy, nowadays a difficult target because of its confident pragmatism.
Liz Kendall with her unarguable, vague 'five causes" seems to have found inspiration from the survivalist instincts of Jim Hacker in Yes Minister. Here they are: Ending inequality, eliminating low pay, building a caring society, sharing power with people and delivering a future of hope for our young people.
Moving on from those bland, apolitical assertions to Andy Burnham. His at least is a more forensic approach - a bit on legal aid here, a bit of rail nationalisation there. Still, not much with which to build the new Jerusalem. Yvette Cooper? Keen enough, it seems, to just be none of the above, so let us not linger there.
But with Corbyn, agree with him or not, there is the sense of someone with an architect's plan for Jerusalem and ready to get the builders in.
Corbyn's critics have tried everything, including mockery, highlighting friends in dodgy international places, and jeopardy, to drown his campaign.
But still attendance at his appearances spill out onto some determinedly unfashionable streets.
His ideas may prove naive, uncosted and unworkable. But that is surely not the point. In a democracy we need to have those ideas for Parliament, us, think tanks and the media to test and be tested by and if necessary to reject.
So three cheers for a politician who is galvanising authentic enthusiasm for a trade held by many in disrepute, even if we never vote him into Number Ten.Suggest a correction