This is a great question. Let me make four points that show the relationship between media and politics.
First, media affect politics, because the media gives incredible access to people of politicians and their politics. In other words, the media has a huge role in making politicians and politics known to voters. For this reason, politicians have to seek to curry favor with the media, so that they would be portrayed well.
Second, the media affect politics, because if the media has a bias, then most likely the media will pass that bias on to its viewers. For example, there is no doubt that the Fox News channel is pro-Republican and very conservative in its outlook.
Third, the media can also have unintended affects. For example, if the media plays something so much, it could wind up making people desensitized to what is going on in the world of politics.
Finally, the media has a huge role in the shaping of public opinion and hence politics when it comes to scandals.