The US midterms campaign is set to be the most expensive on record – with the total cost projected to reach nearly $12bn (£9bn), according to Open Secrets, an independent organisation that tracks campaign finance.
Most of the spending is driven by outside political groups – known as Super Political Action Committees (Super PACs) – pouring large sums of money into some key races ahead of election day on 3 November.
The top individual donor is billionaire businessman Elon Musk, who has spent almost half a billion dollars backing Republican candidates, particularly in Texas, where many of his companies are based.
BBC Verify has looked into the figures and where the money was spent.
