When Lawrence Lessig, the Harvard professor running for the Democratic presidential nomination, scans the Republican field, he sees one obvious ally: Donald Trump.

Trump-Lessig might not be the most natural political pairing of the 2016 cycle. But no other Republican, Lessig said in a phone interview with the Guardian, has been so outspoken on the issue that Lessig has made his own: campaign finance reform.

Lessig has mounted his outsider’s campaign on the argument that corporations and private individuals should not be able to sink limitless money into political campaigns. The practice creates conflicts of interest for elected officials and prevents the work of the people from getting done, Lessig says.

Which is also what Trump has been saying, to a very different audience. Lessig recognized the real estate mogul for the effort when asked whom he sees as a potential partner in a bipartisan effort to pass new campaign finance laws.

“One very important ally has been Donald Trump, who has opened up this issue for Republicans in a way which nobody imagined it was going to be developed,” Lessig said. “He’s made it possible for Republicans to begin to identify this issue in exactly the same way [as Democrats].”

Trump – who slipped behind retired neurosurgeon Ben Carson for the first time in a New York Times/CBS News national poll on Tuesday, with 22% to Carson’s 26% – has hammered rivals for accepting big money from big donors. “I wish good luck to all of the Republican candidates that traveled to California to beg for money etc from the Koch Brothers. Puppets?” Trump tweeted in August, on the topic of a summit hosted by Charles and David Koch, the libertarian mega-donors.

Many of Hillary’s donors are the same donors as Jeb Bush’s—all rich, will have total control—know them well. — Donald J. Trump (@realDonaldTrump) August 5, 2015

Trump has claimed that he does not take donations, as a way of retaining his electoral purity. That’s not true; most of his funding comes from donors, with election commission reports showing $3,817,978 in contributions to him in the third quarter, plus a $100,000 self-contribution by the candidate, against $4.2m in disbursements.

Trump does not appear, however, to be benefiting from Super Pac support or other outside big money donations of the kind that he and Lessig say have corrupting influences on campaigns and candidates.

Unlike his Democratic rivals, Lessig has never held elected office. Nor has he built a national campaign network of the kind associated with a victorious campaign to win a major party’s presidential nomination.

Lessig announced his candidacy in September, after raising more than $1m from small donors. Early on, he offered himself as a temporary president who would resign after signing campaign finance reform law. After he was excluded from the first Democratic presidential debate on 13 October, he threatened to run as an independent and then retracted his pitch as a temporary president.

Lessig has not given up his effort to get into the debates – an effort the Democratic National Committee does not appear to be supporting.

“The whole reason I want to be in this debate is, it’s not enough to say in the abstract that money is a problem,” Lessig said. “What we’ve got to talk about is what the specific answer is.”

Although Lessig has yet to be invited to any debates, he is likely to appear on state ballots as a Democratic primary candidate. About half of the states put candidates on the ballot automatically if they’re discussed in the news media or if they qualify for primary season matching funds, which Lessig has done, said Richard Winger, editor of Ballot Access News, a monthly newsletter devoted to voting laws. Registration deadlines begin to arrive in November, he said.

“There are other states where he can just pay a filing fee,” Winger said. “We’ll just have to wait and see in November.”

Lessig said that he had watched the first Democratic presidential debate and come away disappointed that the idea of public funding of elections had not been mentioned.

“I watched the debate, and I had these two very different reactions,” he said. “On the one hand, I was incredibly excited by the ideas the Democrats were talking about. But on the other hand, I thought that they were ignoring a pretty fundamental problem, which is, we don’t have an institution called Congress that will do any of the things that they’re talking about.

“And that’s not because there are a bunch of Republicans there. It’s because of the incredible corruption of representative democracy that we’ve allowed our Congress to become. The influence of money, and a polarized partisan gerrymandered institution, cannot do what the Democrats are imagining they will do.

“And that’s why I’ve said, we’ve got to start this campaign by focusing on fixing our democracy first.”