It's not about him -- it's what he stands for. Two thirds of Americans don't have an issue with President Obama as a person -- it's not that they really think he's aloof, or too remote, or any of the other stuff which is supposed to be behind his fall in the polls.

It's just that the vast numbers of middle-of-the-road voters across the country are proving more centre-right than centre-left. Health care was one thing - but what's not going down well, it seems, is the President's handling of the economy - from the banking bail out to the still-rising numbers out of work.

When the economy is doing badly - history shows people tend to blame the party in power. And the latest survey show just one third of Americans think Barack Obama has been a "very good" or a "good" president: the rest consider him merely average, or downright "poor".

It's useful ammunition for the GOP, of course: House minority leader John Boehner is making his first major speech of the campaign in Ohio, where he'll focus on jobs: as an aide put it - "the November election will be a referendum on President Obama and Washington Democrats' job killing record." And RNC chairman Michael Steele bashed out an instant response to the jobless figures: "President Obama and his left wing allies on Capitol Hill have spent trillions of taxpayer dollars with nothing to show for it but a mountain of crippling debt and chronic joblessness."

So just over three weeks before the midterms - how should the Democrats fight back? The good news for the party is that barely anyone (just 22%, apparently) - thinks Sarah Palin would make an effective president.

And key election strategist David Plouffe, who's back running Obama's "Organising for America" campaign, has insisted voters are still open to the arguments - claiming large numbers are being put off the Republicans by the success of Tea party candidates.

President Obama himself - and the First Lady, Michelle (now officially the "World's Most Powerful Woman"...whey-hey...) - are out there whipping up enthusiasm on the campaign trail. Even Joe Biden's been sent out on the road, campaigning for 18 candidates in 23 cities across the country - with 18 more events in his busy diary before election day.

And there's a decidely populist tone coming from many Democrats - a direct pitch to working families - hitting Republicans by bashing corporate America, outsourcing of jobs, and the minimum wage.

Yesterday President Obama used his veto to block a bill that sneaked through Congress last week - which critics say would have made it easier for lenders to evict people who missed their mortgage payments. There are legal moves going on in at least ten states to extend a voluntary freeze on foreclosures - with calls for a moratorium across the country.

Union officials from the AFL-CIO have put out literature in Illinois, Oregon and Minnesota, accusing Republican gubernatorial candidates of opposing an increase in the minimum wage - while highlighting other Republican candidates who've proposed doing away with federal minimum wage regulations altogether.

And Democrats in many districts are pushing the message that they're on the side of ordinary workers - a message that pollsters say has been going down well with focus groups. In at least six close-fought Senatorial contests, like California and Indiana - they're putting out campaign ads attacking the Republicans over their record on outsourcing - like this, from Barbara Boxer: "Carly Fiorina laid off 30,000 workers. Fiorina shipped jobs to China."

Not that the Republicans are taking this quietly: a collection of lobbyists from big business called Club Fox Growth is splurging millions on ads in toss-up states which depict Democrats as "out of touch with the financial plight of average Americans." Look at the level of campaign spending, in fact, and you'd be forgiven for thinking the recession never happened...television spending by outside interest groups, says the New York Times, has more than doubled the amount spent at this stage in the 2006 midterms.

But is any of this - from hard cash to populist ads - galvanising people to the polls, and overcoming that much-documented 'enthusisasm gap' among those voters who so optimistically swept Barack Obama into power?

The most recent survey by Pew Research at first looks alarmist - under its banner headline 'Lagging Youth Enthusiasm Could Hurt Democrats in 2010'. But read a little closer - and the numbers are rather more hopeful for the party. Younger voters, it says, are far more supportive of the President than any other age group. 58% of the so called 'Millennial' generation still approve of how he's doing. Of course optimism is the preserve of the young. And three weeks isn't long to turn things around. But still - it might just be too soon to write off Obama - and those "left wing allies on Capitol Hill" - just yet.

Felicity Spector is chief writer and American politics expert for Channel 4 News.