Russia wouldn't be the first country to meddle in US politics - here are 4 other times it's happened

A trove of 20,000 Democratic National Committee emails was leaked last week - and experts are speculating that Russian hackers are responsible.

The Clinton campaign has suggested that Russia leaked the emails to help elect Trump, who has a history of making positive comments about the country and Vladimir Putin. Meanwhile, Trump encouraged any Russians listening to his press conference to find the emails Hillary Clinton deleted from her private server.

If Russia really is trying to skew the presidential election, such interference would be bizarre - but not entirely unprecedented.

In fact, there's a significant history of other countries meddling in American politics to further their own interests.

Here's a look at four times it's happened.