By Kevin Connolly
BBC News, Washington
It is tax day in the United States.
Tea Party protests took place across the United States
Twenty-four hours of annual frustration and dread for law abiding citizens by the end of which they must send to the federal government either a completed tax form or a humble and carefully-phrased promise to do so in the very near future.
There has always been a touch of drama to it - even though millions of Americans complete the forms online these days, some big city post offices still stay open until midnight for tax payers who fancy an adrenaline-charged last-minute drive to meet the deadline.
It has always been a day on which a degree of resentment against the government bubbles to the surface.
That is partly because America's self-assessment system has grown erratically into a thing of startling complexity. The website of the IRS (the agency responsible for collecting taxes) is said to offer more than 560 different forms.
But it is mainly because the United States was born out of a tax revolt (against British colonialism), and many modern Americans retain a kind of instinctive distrust of the whole idea of big government and big taxes.
So Tax Day seemed like an obvious moment for opponents of Barack Obama to take to the streets to register their displeasure at the spending plans he has outlined, not just in his $3.5tn (£2.3tn) budget, but in his stimulus programme ($787bn), the strategic fund for healthcare reform ($634bn), and the bank bailout programme which straddled the end of the Bush years and the start of the Obama administration ($750bn).
It adds up to a projected deficit for this year of $1.85tn - even if Americans all pay their taxes on time.
The protests are being called "tea parties" after the Boston Tea Party of 1773 - when American colonists rebelled against attempts by Britain to impose parliamentary taxes on them without allowing the colonists to be represented in the British parliament.
The modern versions do not quite have that regime-shaking intensity about them.
The protestors at Lafayette Park, just in front of the White House in Washington, were largely middle-aged, middle-class conservatives.
When I arrived, the news was circulating that the authorities had made it known that no actual tea-bags (the demonstrators' favourite props) were to be brought on to the green space outside the White House - no-one seemed to be quite sure what the point of the ban was, or who exactly had imposed it.
But no-one seemed very much disposed to challenge it either, or indeed to mind very much.
The strongest historical link to the original tea party came from David Smith, an anaesthesiologist from Syracuse, New York, who stood out from the umbrella-clutching, Goretex-clad throng in a full George Washington costume - complete with rain-sodden periwig.
This was, he assured me, not about party politics and was not simply a group of disgruntled Republicans getting together to fight November's election all over again.
"George W Bush spent too much money and President Obama is just following suit," he told me.
My sense of the people around me in Lafayette Square... is that they are essentially the kind of people who did not like Barack Obama anyway and certainly did not vote for him
"And they put off the problem by borrowing money so they can keep on giving things to people without having to make hard choices. For me it's not really an issue of Democrat or Republican, it's about preserving the republic."
There were the voices of an older American conservatism there too - a conservatism which does not see much of a role for government beyond national defence and the protection of the constitution - certainly not, for example, in the field of caring for the sick.
David Elliot, a pensioner from Canton, Ohio, would fall firmly into that camp. He is a believer in self-reliance, and he offered this simple diagnosis of what is wrong with Obamanomics.
"Right now it's about spending too much," he told me, "We don't have the money we're spending. We're mortgaging our future. If I ran my household that way, I'd be in debt."
There were plenty of tea parties around the United States, but for all the historical echoes of 18th-Century Boston, there is something about that title that lacks political menace.
And in truth, this is not the kind of political movement that really worries governments (least of all recently elected and still-popular governments like Barack Obama's).
Administrations worry about political movements that suggest a tide is turning and that people who once supported them are changing their minds and switching their allegiances.
My sense of the people around me in Lafayette Square (what do we call them? Tea-baggers? Tea-baggists?) is that they are essentially the kind of people who did not like Barack Obama anyway and certainly did not vote for him.
You got a sense of that from one poster I saw in TV pictures from another rally elsewhere in the country, which mocked one of Mr Obama's favourite campaign slogans: "I'm keeping my money, my guns and my freedom," it read. "You can keep the change."
But the protests do show that opposition to Barack Obama is alive and thriving and that there are plenty of doubts about the wisdom and practicality of the huge programme of borrowing and spending on which he has embarked.
And one more thing. The protests may be an indication that conservatives are starting to wake up to the organisational possibilities of the internet - it is a little late for election 2008, during which the Obama campaign soundly thrashed them in cyberspace.
But even if it was possible to discern the guiding hand of some traditional campaign groups in today's events, there was also a role for grassroots activists talking peer-to-peer on Twitter and Facebook and the like.
They seemed undeterred by the fact that the phrase "tea-bagging" (which has a sexual connotation in some circles) is a bit of a gift to their critics on the left, who are inclined to snigger at them.
Perhaps only viewers of the HBO series Sex and The City will get the reference, however.
The tea-party protesters' new-found web-savvy may be a sign that they are learning from their opponents and preparing for bigger things in the future.
But that will only happen if they can muster the numbers to match those organisational skills - and if the economic conditions provide the right sort of gloomy backdrop for continued protest.