11.20am: Good morning. On the weekend before the US midterms, Jon Stewart, the presenter of the satirical Daily Show, is holding a "Rally to Restore Sanity".

The comedian, who calls President Obama "dude" to his face and gets away with it, has promised nothing more than "fun" for the tens of thousands he hopes to draw to the National Mall in Washington DC.

Some are taking the rally at face value and plan to turn up with banners proclaiming themselves part of the reasonable majority, liberal or conservative, against the rightwing conspiracy theories that have swept America since Obama entered the White House. Stewart himself suggested "I disagree with you but I'm pretty sure you're not Hitler" – a riposte to the president's more extreme critics who portray him as a communist for promoting universal access to healthcare, or Hitler for allegedly planning to impose what Sarah Palin called "death panels" on hospitals.

Stewart has led the counter-attack against conservative broadcasters such as Fox News. Alongside Stewart will be his Comedy Central colleague, Stephen Colbert, whose own nightly show parodies the fear-mongering of Fox News and its presenters.

We'll be following the rally throughout the day. Hadley Freeman will be on one of the Huffington Post buses from New York to the rally and filing her unique take on events. My colleague Richard Adams will take over the coverage once the rally starts.

For a taster of things to come, here's a gallery of the stage being set up.

You can follow the rally on Twitter. The official page is here and this is Stephen Colbert's Twitter account.

12.11pm: US conservatives bloggers are painting the interest in Stewart's rally as further evidence of a liberal media conspiracy.

NewsBusters - "Exposing & Combating Liberal Media Bias" - reckons the 'rally for sanity' has attracted greater coverage than Glenn Beck's 'restoring honour' rally because "the media loves Stewart's leftist message". Writer Lachlan Markay says: "[T]he 'Rally to Restore Sanity' was billed (...) as a counter-punch to Beck's 'Restoring Honor' rally. These are the two camps of political punditry. The mainstream media has clearly picked sides."

Earlier this week, Stewart spoke to the New York Times' Daily Intel blog about organising the rally, particularly whether he risks being perceived as overstepping his role as a political commentator.

"I don't know that it's activist as much as it would be cathartic. Just sending out a little message: There are other people like you who think things are a little extreme. It's not, 'You must vote Democratic, you must vote Republican'. It's not legalize pot or any of that kind of stuff. I still think as long as we do it and make it funny and satirical, we'll be okay. Though I could be kidding myself."

The Christian Science Monitor has a piece assessing whether the rally can in fact restore sanity to America's political dialogue.

On the plus side, it reckons that the vast numbers taking the rally's stated goal seriously is a positive move: "if you look on the rally's Facebook page, you'll find hundreds of people vowing to attend – not in the name of having a good time, but in the name of taking back the nation's politics from what they see as extremists."

But the Monitor suggests there is little chance of the event having any long-term impact:

"US politics today is a 24/7 cable-news carnival, with new acts arriving daily. The Rally to Restore Sanity will appear briefly and then be forgotten as pundits rush to talk about what happened to tea party candidates in the elections."

12.49pm: Hadley Freeman has just joined Arianna Huffington on board the last of 200 buses hired by the Huffington Post to ferry people to the rally. She writes:

Hadley Freeman Photograph: Linda Nylind

"Arianna and I have just boarded the last Huffpo bus and are about to set off from NYC for DC. Even at 5am in freezing Queens, Arianna looked like she was en route to a dinner at a Michelin starred restaurant. I looked like the Michelin man."

The Huffpo's coverage of the event can be found here.

1.35pm: Hadley has just emailed in to reveal she's made Arianna Huffington cry, promising more details in her longer blog on the rally later today. Oh dear Hadley, I hope you weren't mimicking her accent.

For those of you wondering what breakfast is provided on the Huffpo buses: "It's yoghurt - Greek, of course."

3.18pm: Hadley is stuck in traffic en route to the rally:

"Well, there's not much else to do here at the moment on HuffPo Express - we are stuck in badass traffic. So this is DEFINITELY not a political movement - there is no movement at all."

On the plus side, we have a fan:

"Arianna, it turns out, is secretly reading the liveblog! Everyone, wave to Arianna!"

4.03pm: According to Comedy Central, there are already 200,000 people in the National Mall. The schedule for the event has been leaked. Among those taking to the stage are the singer Sheryl Crow and hip hop band the Roots.

Nearly 10,000 people, including our own Hadley Freeman, joined HuffPost's Sanity Bus caravan from New York.

Hadley has been enjoying the autumn colours en route: "This is the prettiest drive ever - we are going through New England just as the trees are at their most multi-coloured and autumnal. I'm the only one who seems charmed by this, though. Everyone else is napping and Blackberrying."

4.21pm: Video from among the crowds gathering at the rally has been posted on YouTube.

There's a bit of a carnival atmosphere with people dressed up as robots and one man with a mohican and a thick gold chain holding a banner saying "Mr T party movement". Well it nearly is Halloween.

4.33pm: OK, I'm handing over to Richard Adams now who will continue our live coverage. Enjoy the show!

11.40am ET: Thank you David and good morning – just – from downtown Washington DC where the streets are thronging with moderate looking people strolling in an interested manner towards the site of today's rally.

I've just come from the Mall and I must say I'm surprised at big the turnout is looking so far. I have to admit I was mildly skeptical that there would be a huge crowd today but it looks like I was wrong.

By the way: we're switching the time stamp on the live blog to Eastern Time, which is five hours behind British Summer Time (which ends tonight and so it will be four hours ... never mind).

11.45am ET: Favourite sign seen down on the Mall so far: "We could be wrong".

11.50am ET: Comedy Central currently showing a repeat of Scrubs. Mm.

Fox News is talking to failed presidential nominee Fred Thompson while showing shots of some Tea Party Express rally of 30 old people waving American flags.

11.52am: Fox News's Neil Cavuto is live from Times Square in NYC for some reason. "Talk about some fine restaurants around here," says Neil.

11.55am ET: Hadley Freeman won't give us any hints about what she did to make Arianna Huffington cry (see the 1.35pm BST entry), although she does deny pulling her hair. "Nor did I mimic her accent."

Seriously, no one can mimic Arianna's unique United Nations accent, so we guessed that.

12 noon ET: And here we go: the rally itself has officially started, with The Roots from Philadelphia on stage. The crowd's looking pretty big.

12.05pm ET: When Glenn Beck's rally was on in DC at the end of August the streets were filled with people wearing "Arkansas Tea Party" shirts and "Don't tread on me" buttons. Today it's a more Timbuk2 satchel and North Face fleece aesthetic (although that's partly a function of the 90F (32C) heat of DC in August and the mid-50s (12C) autumnal weather of October).

If you're still on your way to the Mall, it is mildly chilly, so hats and gloves might be called for. And a soy latte, obviously.

12.10pm ET: Oh look it's John Legend on stage now.

12.20pm ET: For those for you down at the Mall you might like to know that DC's fleet of fabulous food trucks are in the house at the following locations:

Fries: the wonderful Eat Wonky truck is giving away free hot chocolate until 2pm at 7th St between Madison and Jefferson drives (that's smack in the middle of the Mall).

Pizza: DC Slices is at 7th St and Constitution Ave NW – near the National Gallery – excellent thin-crust pizza

Lobster Rolls: Red Hook Lobster truck is also at 7th St and Constitution

Curry: the Fojol Brother's van is at 7th St and Pennsylvania Ave NW, is very fine curry indeed, near the Archives-Navy Memorial metro station

Alternatively check them live on Twitter.

12.27pm ET: My colleague Chris McGreal reports that vast numbers are queuing for buses at the far northern end of DC's Connecticut Avenue, with many in fancy dress – including a group of women dressed as witches holding signs reading " Witches for O'Donnell".

12.30pm ET: A woman walks past wearing a "Taking It Down A Notch" t-shirt.

From the TV coverage there are a number of people in witches hats – it looks like Christine O'Donnell has done more for the image of witches than anyone since Samantha Stephens.

12.40pm ET: In the spirit of mild protest that is the theme of today's rally, this AFP photograph from the Mall sums it up:

Giving Fox News the finger. Photograph: Brendan Smialowski/AFP/Getty Images

The wire caption reads: "A man gestures his middle finger toward a Fox News satellite truck before the Rally To Restore Sanity and/or Fear on the National Mall". Hats off to you, AFP photographer Brendan Smialowski, for this arresting image.

12.45pm ET: "John Legend could do with playing something more up tempo ... I'm not feeling rallied," emails a disgruntled attendee.

And as if on cue, Legend leaves the stage and instead it's the guys from the Mythbusters TV show on the Discovery Channel, doing some orchestrated Mexican Waves with the crowd.

The crowd shots now show it stretching all the way from near Congress, where the stage is, to nearly down to the Washington Monument – that's pretty good. Although compared to Obama's inauguration in 2009 that's pathetic. (That will be the Fox News analysis I'm guessing – although Fox is in fact just ignoring the whole thing today, as is their wont.)

It means it is hard to compare this rally with the Glenn Beck rally for size, because that was by the Lincoln Memorial.

12.53pm ET: The Mythbusters hosts on stage right now, Adam Savage and Jamie Hyneman, are estimating that the crowd is 150,000.

Now they are getting the crowd to simultaneously jump up in the air. "That was 14 trillions times smaller than the 1906 San Francisco earthquake," says the geeky analyst with a laptop.

12.56pm ET: Now it's Jon Stewart coming on stage - typically this rally is actually running early.

There's a sign out the back reading: "Jon 3:16". If you know why that's funny then ... I don't have to explain it. OK, at every public event in the US there is always someone holding up a sign reading "John 3:16", which is the biblical passage "For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life."

In summary: ha.

12.59pm ET: It's the US national anthem. Lots of American flags being waved in the crowd – presumably to be burned later by hippies.

1.01pm ET: "Hello! And are you ready to restore sanity!" says Jon Stewart.

First an important announcement: "No littering," Stewart says. "Are there anyone here who are landscapers?"

"As I look out over here I can see we have 10 million people... and a perfect demographic sampling of the American people. As you know, if you have too many white people at a rally, it's racist. And if you have too many black people, then you must want something."

1.03pm ET: A colleague reports that "Muslims for peace" leaflets are being distributed. (By the time that news gets to Fox News it will have become "Al-Qaida recruiters sign up jihadi volunteers from liberal rally".)

1.06pm ET: Stephen Colbert appears on video trapped in a "Fear Bunker", saying he's afraid that no-one showed up. Is this a Chilean miners reference? Yes – Colbert emerges from a rescue pod underground waving a Chilean flag.

1.10pm ET: "These are reasonable people," Stewart tells Colbert. "They won't be once I release the bees!" shouts Colbert. "You're deliberately created fears of things that don't exist," says Stewart. "No I'm not, I'm raising awareness," replies Colbert.

1.12pm: "If you all don't mind, I'd like to have a more traditional beginning to a rally," says Stewart. "Oooh, a book burning!" says Colbert.

1.15pm ET: There's a benediction – which thanks God for making it easy to find parking spaces.

1.20pm ET: Here's a shot from the front of the stage:

The crowd seen from the front of stage at the rally. Photograph: Jim Bourg/Reuters

That's the Washington Monument poking up way in the back. Signs include "Moderates do it both ways" and "Rally to restore manatee".

1.29pm ET: Ozzy Osbourne and Cat Stevens/Yusuf Islam appear on stage in perhaps the world's least likely duet. "Stop, stop, this is not right!" shouts Stewart as the pair do duelling train songs – Osbourne doing Crazy Train and Yusuf doing Peace Train.

Then the O'Jays solve the problem by appearing on stage singing Love Train.

1.35pm ET: It sounds like the size of the crowd has overwhelmed the expectations of the organisers. My colleague Chris McGreal reports from the Mall:

Large numbers of people leaving because the crowd is so large they can't hear. Not enough speakers.

1.40pm ET: Top sign seen in the crowd so far: "The Founding Fathers were East Coast liberals".

My colleague Paul Harris – at the rally for the Observer (reserve your copy today!) – emails:

"Thousands of people are still arriving. An hour after it started the subways trains are still packed like sardine tins and everyone gets off at the rally stops apart from a few bemused locals."

1.42pm ET: How is Fox News coping with this competition? Right now on Fox News they are interviewing the former deputy campaign manager for Mitt Romney's 2008 failed presidential campaign. How can Stewart's rally possibly hope to compete with superstar spoilers like that?

1.45pm ET: Stewart and Colbert are now awarding medals, Colbert's being medals for fear. He wants to give the first medal to the news media organisations that banned their staff from attending, especially National Public Radio (NPR). But none of their staff will be there. So he gives the award to someone with more courage: a seven year old girl.

1.49pm ET: On Twitter, a sour note from Peter Daou, who ran Hillary Clinton's online presidential primary campaign:

Great turnout, but so far the #rally4sanity seems aimless and unfunny. Stark contrast with Beck's sinister legacy theft & co-opting of honor

1.57pm ET: In some ways this rally is a mirror of the Daily Show and Colbert Report – the principals are very funny but the supporting cast are ... not so good.

2pm ET: While Stewart and Colbert are duetting, Paul Harris reports some fine signage among the crowd:

"Pay taxes. How else do roads get built?"

Paul notes:

"It is actually quite jarring and very good to see signs calling for more taxes and pointing out what they do. You literally never see that at political rallies, though obviously at Tea Party ones they are there all the time."

Other beauties include: "Ask. Tell." (A reference to "Don't ask, don't tell". Apologies if you knew that already. Which most people would. So, uh.)

2.05pm ET: "I'm very sorry you had to hear me sing," says Stewart after the duet ends.

Other top signs include one written above the classic hissing snake "Don't Tread On Me" poster so popular with Tea Party types: "Snakes! Watch out snakes!"

And another one, written above a picture of a cuddly bear: "Brutal killing machine". (A regular Colbert riff is about his fear of bears.)

My personal favourite: "If your idea can fit on a sign, you need a bigger idea."

2.15pm ET: Here's Sheryl Crowe and, ah, Kid Rock duetting.

On the fringes of the crowd quite a few are said to be leaving because they can't see or hear anything. Such is the nature of a Washington DC rally, my friends.

2.18pm ET: Another top sign seen in the crowd:

"War is not free. Teabaggers, pay your taxes."

There's a pro-tax meme going on. Typical Democrats – as Fox News would say if they weren't just stone-cold ignoring this event.

2.29pm ET: Getting slightly more serious here after Colbert introduces what he says is an important announcement: a brief clip of Stewart acting in the 1998 movie, The Faculty.

Stephen Colbert (left) and Jon Stewart debate reasonableness. Photograph: Kris Connor/Getty Images

Stewart prepares to give a keynote address about reasonableness, but Colbert instead wants a debate. Colbert demands to be "empodiumed."

After Colbert claims that all Muslims are scary, Stewart produces famous basketball icon Abdul Kareem-Jabbar (who British readers may know as the co-pilot from the movie Airplane!) "Your reasonableness is poisoning my fear," Colbert tells Stewart.

2.35pm ET: Colbert "unleashes the media" showing a fantastic series of clips of shouty talking heads on cable news TV, including the worst bits of Keith Olbermann, Glenn Beck, Ed Schultz, among others.

Update: Olbermann was not best pleased that he appeared in Stewart's Hall of Shame here, tweeting: "It wasn't a big shark but Jon Stewart jumped one just now with the 'everybody on [?] cable is the same' naiveté".

Olbermann works for MSNBC and would like to think he's above the Fox News fray but he's cut from the same cloth – and that's Stewart's point.

2.40pm ET: R2D2 appears on stage as an example of a reasonable, non-scary robot.

2.47pm ET: Stewart now giving a stirring and serious summing up to conclude things. "So what exactly was this?" he asks. Here are the highlights in what was a curiously moving and effective speech:

"We live now in hard times, not end times. And we can have animus and not be enemies. But unfortunately one of our main tools in delineating the two broke. The country's 24 hour political pundit perpetual panic conflictinator did not cause our problems. But its existence makes solving them that much harder. "The press could hold its magnifying glass up to our problems, bringing them into focus, illuminating issues heretofor unseen. Or they can use that magnifying glass to light ants on fire. And then perhaps host a week of shows on the sudden, unexpected, dangerous flaming ant epidemic. If we amplify everything, we hear nothing."

"We hear every damn day about how fragile our country is ... and why don't we just work together to get things done. The truth is we do, we work together to get things done every single day. The only place we don't is here [Congress] or on cable TV. But America doesn't live here or on cable TV."

Stewart used an extended metaphor about drivers going through the Lincoln Tunnel under the Hudson, in front of clips showing traffic moving through the tunnel's entrance.

"Sure, at some point there will be a selfish jerk. But that individual is reviled, he is scorned, and he is not hired as an analyst. "Sometimes the light at the end of the tunnel isn't the promised land – sometimes it's just New Jersey."

Two lines there for the Oxford Book of Quotations: "We live now in hard times, not end times" and "If we amplify everything, we hear nothing."

2.54pm: Jon Stewart winds up: "Sanity will always be, and has always been, in the eye of the beholder. To see you here today has restored mine."

Then he introduces Tony Bennett to sing "God bless America". The crowd chants "USA, USA, USA" as is traditional whenever more than two or three Americans are gathered together near a TV screen.

2.58pm ET: The whole cast is being brought back on stage by Stewart and Colbert for a final big number – and that's it!

Comedy Central immediately switches to Hot Fuzz starring Simon Pegg. So there was a comedy British connection of sorts. John Oliver doesn't count because he's not actually funny.

3.02pm ET: Well then, wasn't that interesting? It reminds me of the old joke: "What do we want? Moderate change! When do we want it? In the medium-term if resources permit!"

3.15pm ET: Can we possibly sum up the spirit of the Stewart/Colbert rally in a single picture? Yes we can.

A message to remember from the Stewart/Colbert rally? Photograph: Grace Miller (available for weddings and bar mitzvahs)

What more is there to say?

'But not usually at the same time.' Photograph: Nicholas Kamm/AFP/Getty Images

So the "I masturbate and I vote" thing was a popular sign. Well, it is a popular practice. Voting, that is.

3.25pm ET: The crowd is moving off the Mall into what looks like an impromptu parade up Pennsylvania, heading for the White House...

Meanwhile, Simon Pegg tweets: "I apologize for interrupting #rally4sanity on Comedy Central with Hot Fuzz. It was not my decision. I'm not insane."

3.45pm ET : Mollie Hemingway is tweeting photos of some of the more bizarre, random and interesting signs being seen at the rally today:

Thou shalt not be douchebags

I prefer facts nuance and intellectual debate so I'm probably not a real American

Strange mama grizzlies distributing endorsements to constitutionally challenged witches is no basis for a system of government (Monty Python's Holy Grail reference there.)

Help! Sarah Palin STOLE my cane

Iraqi-American: I'm afraid to get on a plane with myself

3.56pm ET: Finally, an answer by the Guardian's Hadley Freeman to "Cry-gate" – revealing how she made Arianna Huffington cry on the bus journey from NYC this morning:

Arianna and I finally got on the last bus and, over breakfast, (yoghurt – Greek, of course) talked about the rally. And it was at that point that I made Huffington cry and, to make matters worse, I didn't even notice I did it.

Read all about it on Hadley's excellent blog.

4.28pm ET: Oh hey, Fox News finds time in its busy schedule to cover the rally. "Some were just there for an afternoon of fun entertainment..." is the lead in, and a couple of interviews.

The Fox anchor named Gregg ends with some snark: "Jon Stewart poking fun at the news, I'm shocked, I'm stunned, how incredibly novel of him." And that's why you're on the high-profile Saturday 4pm slot, Gregg.

Later, after his co-host mentions it was called the Rally To Restore Sanity, Gregg snips wittily: "I liked insanity better." I bet you do Gregg.

4.38pm ET: Waiting on the Stewart and Colbert post-rally press conference.

4.49pm ET: MTV Networks say they estimate the crowd to have been 250,000. (Estimating the size of a crowd bigger than few hundred is the way to madness.) And that might explain why no one could hear anything at the back – Comedy Central was only expecting 60,000 in its permit application.

Comedy Central said it counted about four million hits on its website's live stream of the rally.

5pm ET: Hmm. Asked at the post-rally press conference if he thought people should vote, Jon Stewart rather tepidly replied: "I think people should do what moves them."

5.24pm ET: Mainstream reaction is coming in – and the best thing about this Politico piece is the shot of a sign reading "God hates figs":

For most of the rally, Stewart and his comedic foil Stephen Colbert deftly remained half a step away from becoming serious on the stage at the opposite end of the Mall from the Lincoln Memorial steps where Beck spoke — until the end, when Stewart aimed his wrath directly at the 24-hour Washington media establishment, saying it "did not cause our problems. But its existence makes solving them that much harder."

5.39pm ET: The New York Times goes for crowd scene colour:

Though it was billed as a gathering for civility – a party on a sunny Saturday for people to enjoy thoughtful conversation – for participants it was a serious political affair. Some were canvassing for votes. Others were searching for a message they felt had been lost by Democrats since President Obama was elected in 2008.

6pm ET: The normally deserted streets of Washington DC are still filled with people making their way back from the rally.

In the words of Jon Stewart, "So what exactly was this?" It's hard to say really – it was a fun day out if nothing else. But it was also something quite important, after nearly two years of watching the likes of Beck and the Tea Party hold attention-getting rallies, to show that they are not the only ones who can do that, and that people want to have their voice heard but they don't need to shout to do so.

Thanks for reading.