Well, so much for the idea that Hillary Clinton has already locked down the presidency.

Just as it looked as though her lead in the polls was insurmountable, along comes the director of the FBI to announce that the email controversy that has dogged her throughout the campaign remains alive and well.

You couldn't make it up. Or, rather, if you did pitch the tale of this election as a story to a TV network, you'd be told to go away and not come back until you had devised a more realistic scenario.

The clever money is still on Clinton to win next week, but she's in for a rocky few days.

One advantage she has is that millions of early votes have already been cast. For those voters, no news event between now and election day can change how they cast their ballots.

Furthermore, there's the familiar dichotomy between the national polls and the state polls. It seemed over the weekend that Trump was getting closer to Clinton's numbers on a national level, and had perhaps even pulled ahead in the crucial state of Florida. But Clinton remains ahead in the important states of Colorado, Pennsylvania and North Carolina. As we infamously saw in 2000, winning the popular vote and winning the right states can be two very different things, so Trump should be more concerned about the individual battleground polls than the headline national figures.

What Clinton should be worried about is the motivation of her supporters. There has been so much noise, so many wild claims and so much hatred swirling around during this election that it's unlikely anyone who is firmly in either camp will switch horses now. It's hard to see how the weekend's email shenanigans could make someone start to doubt Clinton for the first time - goodness knows there's been enough said about her already.

But she was already facing an uphill battle to re-create the fervour of Barack Obama's supporters during the past two presidential elections, and the risk is that recent events make some of her existing backers decide to sit the whole thing out.

There is a huge 'none of the above' contingent who can't stand either candidate, and Clinton should be worried that the latest controversy will add to that.

On the other side, of course, there's Trump. Having claimed that the FBI was part of a huge cover-up when it previously failed to prosecute Clinton over the use of her private email server, he's now heaping praise on FBI director James Comey for reopening the investigation.

(Funny, isn't it, how both sides think people who agree with them are patriots while those who don't follow a certain course of action are traitors or part of a conspiracy?)

Trump has been at the centre of far more controversies than Clinton during the course of the past year, but sometimes it's the most recent event that sticks in the memory the clearest.

That, in the short term at least, gives an advantage to Trump. Don't bet against him scoring another own goal soon, but if he can stay on message and allow the spotlight to remain on Clinton and her woes, things may yet tighten further before election day.