I'm just back from visiting Washington DC for the first time, it's an extraordinarily beautiful city and the view from Capitol Hill is stunning.

A stroll along The Mall from the Lincoln to Washington memorials, taking in national monuments such as the Roosevelt Memorial (a real highlight) and the Vietnam, Korean, and Second World War monuments is a lovely way to spend a day. There isn't a piece of litter in sight. Every view of the city is practically postcard worthy. Outwardly it looks perfect.

Yet even Washington has the same creaking infrastructure as the rest of the country - the entire Metro system was shut down for 24 hours because of an electrical fault. DC both masks and highlights the great contradiction that is the real America.

It is a country born by overthrowing the monarchy and standing tall against divine and unlimited power placed in one man - but also names its capital city, a state, and a monument after one man. An (admittedly exquisite) mural on the roof of the rotunda in Capitol depicts Washington as a saint ascended to heaven.

I visited the National Archives which hold the originals of America's three key founding documents - The Declaration of Independence, The Constitution, and The Bill of Rights. They are interesting documents to view but Americans in the room were audibly gasping in amazement at being three feet of glass and two armed guards away from these hallowed documents.

The Seal of the United States includes the phrase 'E pluribus unum' - (Out of Many. One). But there is too much dividing America for it to be truly united; too much pride in being the "great experiment" to truly allow the system to be challenged. All that has been done politically for generations is to tinker around with the founding documents lest having a good hard look at the way they organise their politics consigns the experiment to the scrap heap.

Which is probably why the Establishment in both the Republicans and Democrats are so worried about the mavericks Trump and Sanders (it comes to something when the pale, stale, males are the mavericks but, like I said, it's a nation built on contradictions) and what their campaigns are going to uncover.

In Sanders versus Clinton you couldn't have a more radical versus establishment contest. Sanders's role in the race was supposed to be to draw Clinton left on issues such as the economy, to give a good account of himself in place of the true darling of the left Elizabeth Warren, and delay slightly the inevitable Clinton coronation. Instead, his has been a real challenge and while she is still in pole position following the New York primary, a close run-in or even an unlikely defeat, would send her campaign team - and the Democratic Party - into disarray.

Sanders advocates a "political revolution which revitalises American democracy". Openly. He says it all the time, like it is something he truly believes. And that terrifies the Democrats.

They remember how it went the last time they went to the polls with a principled man selling a message of hope and change to the nation. He won. He's still President. And bar a nice wee period where the Dems had a majority in the House and Senate (and then got humped) he's been bogged down in partisan bickering on the hill for the majority of his time in office and the country is more divided than it has been before. So much so that the Republican frontrunner is billionaire, man of the people, Donald Trump.

Obama's actions have been unable to match his searing rhetoric and verve because the whole political system of the country is built so that no one can.

The party wants Clinton because she can work within the current structure, and make a good fist of it. Clinton the Competent beats Sanders on his Soapbox any day of the week.

What they don't want is someone that will try to start a revolution. Who will lift the bonnet, take one look and write it off and then, argue you could go a lot further, faster and more comfortably in a whole new model.

What if Americans agreed and started to want a better model too? Too much money has been spent, and too many people have been made extremely rich by this old American banger for it to be replaced now.

Plus, revolutions sometimes get messy, often in capital cities, and Washington DC is far too pretty to have that on its doorstep. The system thrives on good, able, safe candidates like Clinton, they'll do everything they can to get her elected. The future of their great experiment depends on it.

Kirsty MacAlpine works for a health charity. She has previously worked in the Scottish Parliament. You can follow her on Twitter @KirstMacAlps.