NEW YORK: An extra $55m, at least, has been spent on political advertising on TV and radio in the two weeks before the US presidential election, but media companies are now having to prepare themselves for a potentially very different post-election landscape where audiences are expected to decline.

According to Advertising Age, Donald Trump's campaign and associated political action committees (PACs) invested an additional $24.2m in the ten days to last Friday, while the corresponding increase for Hillary Clinton's campaign and PACs amounted to $31.5m.

It also reported that total presidential campaign TV and radio ad spending – including all the dropouts and the primary season – now ran to more than $1bn.

Media companies haven't always benefited from political advertising expenditure this election season but have gained ratings: for long periods the Trump campaign, for example, spent very little as the candidate's controversial public pronouncements kept him centre stage and kept viewers tuning in.

Politics-based sites have also reported a surge in visitors. Politico now has more than 20m unique users in the US, more than double the figure of last September according to comScore data, while FiveThirtyEight has seen a 61% increase to 8.7m.

Nate Silver, editor in chief at FiveThirtyEight, told the Wall Street Journal that that figure would fall back after the election but he hoped it would stabilise at a higher figure than before.

"Politics is a great way to introduce people to your brand," he said. "How we transition that audience is something we have to think about."

Other media companies are contemplating a similar scenario. "There's no expectation that the ratings in 2017 will be what they were in 2016," said Allison Gollust, EVP and CMO at CNN Worldwide, as she outlined how the business planned on retaining its new viewers.

"One of the things we really tried to do with the momentum we had this year was to promote our original series and films," she explained.

It is of course quite possible that the new audiences media owners have acquired are not about to fade away since the political environment is not going to become any less febrile any time soon.

As Steven Ginsberg, senior politics editor at the Washington Post noted: "Whoever wins is not going to be seen as legitimate by a lot of the country. The 2020 campaign, I shudder to say it, has already started."

Data sourced from Advertising Age, Wall Street Journal; additional content by Warc staff