In the light of your book, Nation on the Take (How Big Money Corrupts Our Democracy and What We Can Do About It), what do you make of this current presidential election? Are there any surprises in terms of funding and expenditure of the candidates?

I think that the popularity of Bernie Sanders has been very interesting and surprising. I think it shows that there is a lot of support for candidates who are not on the take, who do not seek big donations from corporate interests and billionaires. And I think even the rise of Donald Trump is interesting in that people are attracted to his campaign because he’s not taking money from special interests, corporations and other wealthy people. I think the common trend is that people are really fed up with the money-driven aspect of American politics. Whether you’re on the left or right, people want to see things change.

Wendell Potter, co-author of Nation on the Take. Photograph: Alex Wong/Getty Images

Sanders has pointed out that Hillary Clinton has taken money from Wall Street. Has that had a serious political impact?

I definitely think voters have noticed that. I think it’s one reason why Bernie Sanders continues to be a contender and why Hillary Clinton hasn’t sewn the nomination up yet. I think there are a lot of Democrats who are concerned about money and politics; even though she says she’s not influenced by people who give her money, there is a concern that it would be a continuation of the same old same old. That said, on her campaign platform, she says she wants to reform the system and get big money out of American politics. To get elected, you have to play the game as it’s currently played. She may be right about that. She may well end up being the Democratic nominee, but I think there will be a lot of people who hold her to her word on reforming the political system.

What has been the biggest contribution to the corruption of the US political system?

The unrestricted growth of money in politics. The ability of a few billionaires, a few very wealthy families and individuals to inordinately influence elections and public policy. We’ve had similar times in our past when we’ve got to this point and we’ve had corrections. President Teddy Roosevelt, for example, was probably our country’s most vocal champion of campaign finance reform. He was able to rally public support and push forward reforms that were very important in bringing an end to the gilded age. What we have now is a second gilded age and it’s because some of the laws that were passed have been unravelled or amended.

Why do US election campaigns need to be so long? Could they be shortened?

I think it’s possible. That is absolutely something that we as a country should take up. I think there is probably the assumption by a lot of reformers that it’s an area we just can’t tackle at this point because the various states set their primaries early on so that they can have more influence on the outcome of campaigns. We should look at the elections in the UK and Canada.

Bernie Sanders on the campaign trail. His support has been bolstered by voters fed up with the influence of big business on politics. Photograph: Matthew Cavanaugh/Getty Images

Your book argues that it’s not just voters but politicians themselves who are fed up with their onerous fundraising duties with the rich and powerful. So why is so little done about it?

Politicians are fed up. They do not like having to leave their offices on Capitol Hill and go to another building where they can legally sit in a cubicle and dial for dollars for hours on end. But they don’t as yet see a movement [against this] that’s taking shape. We need a groundswell of support and also support from the elite in the country. It’s going to take a coalition of grassroots and grasstops advocacy.

How long will that process take?

I don’t see a reason why we can’t see significant change in five years from now. Legislation can be introduced and enacted in a very short period of time. Look at how rapidly things changed on the issue of marriage equality. We’re seeing things change much more rapidly partly because of the ability of people to communicate more effectively in the internet age.

The supreme court Citizens United decision was a controversial ruling. Can you explain its impact?

That ruling and others, which said that Super Pacs [independent groups that collect donations in support of candidates] can receive unlimited contributions from individuals and corporations and labour unions, opened the floodgates of money into politics. And these groups are unaccountable. They don’t have to disclose their donors. They have come to influence voters’ decisions and policy decisions in ways that didn’t exist previously. We now have little knowledge about who is trying to influence public policy and elections. That needs to be changed.

The rise of Donald Trump has also been put down to an electorate that feels ignored by Washington’s money men. Photograph: Charles Rex Arbogast/AP

Republican backers the Koch brothers, you say, have forged a small network of the very wealthy to spend nearly $900m to influence the outcome of this year’s elections. Are they having any success?

A lot of people look at the success of Donald Trump and the demise of Jed Bush’s campaign and say that shows you money can’t buy elections. That’s not true. That obscures the fact that enormous sums of money from the Koch brothers and others are able to influence congressional and state elections. Most of the money they spend goes to organisations that are very active at the state level. But it’s extraordinarily important because the states determine the House of Representatives, which is largely in control of the Republican party. And in most of the state capitals the governorship and the legislature are controlled by conservative politicians. So you shouldn’t underestimate the influence of the Koch brothers.

What’s been the feedback on your book?

We’ve had extraordinarily good reviews. We’ve had good audiences on our book tour. What’s been really gratifying is the support we receive from Republicans as well as Democrats. If we’re ever going to make progress it’s going to have to be on a bipartisan basis. One thing on the negative side is I think the book would be getting even greater recognition if the American media weren’t so completely obsessed with Donald Trump’s campaign. One producer told us we’ve been Trumped. The media are hardly covering anything else.