The tight battle for South Thanet is causing tempers to fray on polling day

The tight contest for the South Thanet seat caused tempers to fray on polling day with accusations of intimidation and verbal altercations on the streets of the constituency.

On Thursday, Business Insider witnessed verbal altercations in Ramsgate between a small group of UKIP supporters and passers by not far from the party's office there. Elsewhere, the Guardian reports that the local Labour party has made formal complaints to the police over four incidents of intimidation by UKIP supporters outside of polling stations, although a Labour spokesperson told us that he was aware of "at least five such incidents".

And the problems aren't solely on UKIP's side. UKIP candidate and party leader Nigel Farage claimed on Twitter that one of his party's "higher profile members" had their window smashed with a plant pot in the early hours of the morning.

I'm sad to say that last night one of our higher profile members' had their window smashed with a plant pot at 3am. #SouthThanet #ivoted

- Nigel Farage (@Nigel_Farage) May 7, 2015

Tensions are running high in the tight race, and the stakes for UKIP are particularly high. Farage has said that if he loses the seat then he would resign as party leader, saying it would be "curtains for me".

Such a result would be a bitter blow for a party that has leapt from near obscurity to potentially becoming Britain's third largest party by vote share with the party projected to win around 12% of the national vote. If the party are to cap that surge with tangible results in the House of Commons, however, South Thanet it is a must win.

There's only one problem - the Conservatives have been holding a lead in the polls since last November:

So it is perhaps unsurprising that the mood on the streets is tense among UKIP supporters. They have thrown everything at the campaign, including dominating the local billboards and drafting in supporters from all over the country on the weekend to launch one final push to get Farage to Westminster.

Party officials told Business Insider that their own internal polling was pointing to a good result in South Thanet, but that is hardly a surprising message to be coming out of the camp. The Conservatives were equally bullish on their chances.

What will likely decide his fate now is whether voters decide to vote tactically at the last minute. As you can see in Lord Ashcroft's polls above, the Tories have gained from a decline in Labour's vote share.

That could suggest, in the words of Lord Ashcroft himself, "that Labour supporters may be lending their vote to the Conservatives to stop Nigel Farage".

Of course, that swing remains modest so far and the distance between the Conservatives and UKIP is still within the margin of error so the seat remains a tough one to call. There will be more nervous times for UKIP's self-titled "People's Army" in the coming hours before the result comes out at around 6 a.m. tomorrow.