At the time of writing, neither Nigel Farage nor Marine Le Pen has been assassinated, though Mr Farage's car was sabotaged, in France, in a clear attempt to kill him. A blog on this subject is always in danger of being overtaken by events, though. Whoever was trying to kill Mr Farage wasn't a lone nutter doing it for notoriety, because they chose a method: loosening ALL the wheel nuts, which allowed them to escape unseen and unsuspected. More of an organised attempt than a deranged man's try for glory. It most probably took more than one person to loosen so many bolts in the available time window.
The purpose of this article isn't to recite methods of assassination, but to explore who might want to do it. In Britain, political assassination has mainly been the goal of dissident Irish Republicans rather than any of the main political parties, with one (possibly two) important exception(s). The Conservative party has no history of actual (rather than figurative) political assassination, and pending a full and fully public inquest into the death of Dr David Kelly, backed up by appropriate scientific investigation including as suggested here, neither has the Labour party. The one mainstream British political party which does have a history of hiring hit men is the Liberal Democrats (in their former incarnation as the Liberal party) and that is also the party which is the most unreservedly pro-EU. None of the mainstream political parties in France has a recent history of assassination, though there were several plots to kill General De Gaulle some decades ago. The plots to kill De Gaulle seem to have engendered a lasting distaste for assassination amongst French politicians.
It is obvious why Mr Farage's British enemies want him dead: he is the figurehead of British opposition to EU membership, and none of the other "Brexiteers", including Boris Johnson, have Mr Farage's level of political talent and dedication. The likely payoff for the assassination of Mr Farage would be a divided and ineffective pro Brexit campaign, which would fail to successfully resist the plan by the former Labour leader, Tony Blair, and the former Liberal Democrat leader, Nick Clegg, to reverse the referendum result and have Britain stay in the EU despite the democratic vote to leave. When Pin Fortuyn, the nearest equivalent to Nigel Farage, was murdered in Holland, there was a national outcry, but nothing very much in the way of violent political backlash and the country's political elite were not seriously threatened. The British public is no more skilled in flaying politicians than the Dutch public: Mr Farage's death would cause an outcry but the political elite would probably be able to ride out the storm. There would have to be a scapegoat though!
It is less obvious that French opponents of Marine Le Pen, a popular Joan of Arc figure, would want her dead, because there would be a tremendous public backlash if she were assassinated or if it even just seemed that she was. The French public is skilled in taking to the streets and flaying politicians. Nobody living in France would want to risk the consequences. But Ms Le Pen poses a problem for anyone in Britain wanting to do away with Nigel Farage and reverse the democratic vote to leave the EU: if she is elected president of the republic next year, France will leave the EU and that means that the show, and the Brussels gravy train, is over. There would be nothing left to coerce Britain into continued membership of.
Someone is trying to kill Mr Farage and that someone is capable of arranging an attempted hit in France. There is no payoff for any likely conspirator in assassinating Mr Farage unless something is also done to neutralise the existential threat to the EU posed by Ms Le Pen. Whoever is responsible for Ms Le Pen's security needs to be very much on top of his game. Her security people need to be alert to threats from outside France, too.
Footnote: The Murder of Jo Cox MP
Jo Cox MP was not killed on the orders of Nigel Farage or any other Brexit leader: they had barely heard of her before her death. She was killed by her constituent, Thomas Mair, who subscribed to a lot of very right wing and racist material but who made no response when invited to actually join an extreme right wing group that held a recruitment meeting in his locality. Despite what Mair said at the time of the murder, his biggest grievance seems to be largely personal in that he was being asked by the local council to leave the house he had lived in since childhood. He saw that as being thrown out of house and home to make room for immigrants, and there might even have been a tiny grain of truth in that: he was being thrown out to make room for someone else who would make full use of a three bedroomed house. But the root cause of his misery was a faceless bureaucracy that he couldn't do anything to hurt, so he turned on his MP, who was identifiable and much more accessible, and had championed the cause of refugees, which in his mind became associated with losing his home. Authorities need to be more aware generally that losing a home produces a big emotional reaction in most people, let alone the mentally disordered. Mair now has a home in prison for life, which may actually be what he intended. He certainly made no attempt to avoid arrest whatsoever.
The element of conspiracy exists because the police don't believe that he stole and modified the gun used in the murder himself. It is hard to know what the person who did modify the gun was thinking of, because the barrel of the .22" rifle was cut down so short that it would only function as a weapon at point blank range. The only likely possibility that the blog author can think of is that the rifle was sawn off to make it effectively a humane killer for use on trapped large animals such as deer. That would make it a bit of poacher's kit. How Mair would have obtained it is a matter for speculation, but anyone knowingly equipping him for a murder wouldn't have clipped the barrel quite so short, and would most likely have supplied a different firearm altogether. Mair seems to have been aware of the gun's deficiencies because he tried to research whether a .22" bullet to the head would be fatal, and he took a knife with him as well, and made a point of using it.