It's been another dramatic few days in the marathon that is the US presidential election.

And, for about the first time during the campaign-proper, it's been Hillary Clinton who has been forced on to the back foot.

There had already been mutterings by conspiracy theorists that Clinton had health issues that should have ruled her out from being president. That in itself was no surprise – Donald Trump has made a career out of giving support to some of the more ridiculous theories that fly around the internet.

He has been a key player within the Birther movement (those who believe that Barack Obama is an illegitimate president because he apparently was born in Kenya rather than the US), only on Friday – after years of pushing the conspiracy – admitting that it's a load of nonsense.

He has also propagated the myth that thousands of American Muslims were seen celebrating as the Twin Towers came crashing down in 2001 – a 'fact' that no one has managed to find any evidence for.

So it has been no surprise that stories about Clinton's health have taken on a life of their own within the fanatical Trump base.

But then, last weekend, there was finally some real evidence that all might not be right with the Democratic candidate's health. Having left a 9/11 ceremony early after feeling unwell, she was videoed stumbling and having to be helped into her motorcade by Secret Service agents.

She has since claimed that she was suffering from pneumonia and had simply ignored her doctors' advice to take some time off – but it all plays into the narrative that she has issues that make her unfit to be president.

It's also played into another narrative – the belief held by many voters (and not just her political opponents) that the Clinton machine is highly secretive. Time and again over the past few months, getting information from her campaign has been like pulling teeth. Denials are followed by half-announcements, which are then followed by clarifications and, finally, by claims that everything is a vast right-wing conspiracy against her. She refuses to hold press conferences.

It has all meant that Trump has cut Clinton's lead over the past few days. He is leading narrowly overall in some polls, and in the battleground states there is less distance between the two candidates than there was.

Another apparent recent faux pas was Clinton being caught on tape having a not-so-subtle dig at Trump's base.

'You could put half of Trump's supporters into what I call the basket of deplorables,' she was caught saying. Cue more fury from the Trumpsters.

Many commentators declared this to be another huge gaffe by Clinton, comparing it to Mitt Romney's '47pc' comment four years ago.

On that occasion, Republican candidate Romney was recorded at a behind-closed-doors meeting saying: 'There are 47pc of the people who will vote for (Obama) no matter what ... who are dependent upon government, who believe that they are victims. These are people who pay no income tax ... and so my job is not to worry about those people. I'll never convince them that they should take personal responsibility and care for their lives.'

In one fell swoop, by suggesting that nearly half the electorate are on the take, Romney managed to alienate millions of people in the centre who might otherwise have voted for him.

Clinton's comment this week, though, was aimed only at Trump's supporters rather than at the electorate as a whole – and it's not as if many of those who have already aligned themselves with the colourful businessman were likely to switch to Clinton anyway.

So despite all the brouhaha that the comment caused, it's unlikely to damage Clinton amongst her likely supporters. Her health issues might, though, as might the lack of transparency her campaign has displayed.

Her team will point out that despite their recent troubles, Trump has had far more bad weeks than they have. They will be expecting (and with good reason) their opponent to score another own goal fairly soon.

But this week needs to be a lesson for Clinton. Whatever her lead in the polls, a couple more crises and the perception of losing control could make this race more open than she had expected it to be.