Harvard law professor and longtime campaign finance activist Lawrence Lessig announced Tuesday that he was exploring a presidential bid in 2016 in order to highlight the need for federal campaign finance reform.

Lessig, if he makes a long-shot play for the Democratic nomination, is by his own admission a single-issue candidate, focused solely on reducing the power of big money in American politics.

In a conference call with reporters Tuesday morning, he said he would frame his candidacy as a national referendum on campaign finance and will formalize his presidential campaign if he can raise $1 million by Labor Day.

Although most of the major candidates running for the Democratic nomination —including former Secretary of State Hillary Clinton, Vermont Sen. Bernie Sanders and former Maryland Gov. Martin O’Malley — have also expressed their strong support for campaign finance reform, Lessig said none of them are making it a top priority or presenting a plausible plan for reform.

“The first thing we have to think about is, ‘How we can unrig this rigged system?’ But this is the one thing that none of the candidates have yet articulated,” he said. “How will they unrig the rigged system first so that the other things they are talking about are credible?”

Making an unorthodox campaign promise, he said that if elected, his first and only act as president would be to pass a package of reforms, titled the Citizen Equality Act of 2017, that would rein in big spending, change the way federal elections are funded, address congressional gerrymandering and expand voter access. Once the bill is passed, he vows, he will resign and allow his vice president take over.

“I want to be a president as short a time as possible,” Lessig said, noting that campaign finance reform is an issue that cuts across partisan lines. “This is an idea that could rally people to produce the mandate that would actually make it possible to pass reform.”

In the wake of the 2010 Supreme Court decision Citizens United v. FEC, spending on elections has ballooned, much of it in the form of expenditures by outside groups that can easily avoid disclosing their donors under current campaign finance laws. In the 2008 presidential and congressional elections, such expenditures totaled $143.6 million, according to data compiled by the Center for Responsive Politics. In the 2012 elections, outside spending hit $1 billion.

Lessig said the current system amounted to blatant corruption and that other proposals favored by liberals to address income inequality or climate change could not move forward until members of Congress were freed from the undue influence of special interests and wealthy donors.

He is no stranger to long-shot political experiments. In 2014 he launched May Day PAC, a super PAC with the goal of electing a pro-campaign-finance-reform majority in Congress. Although the group raised millions of dollars, it managed to elect its chosen candidate in only two of the eight races in which it was involved.

Lessig said he has learned lessons from the May Day PAC and believes that this time, he has a tangible plan for reform that Americans are more likely to embrace.

“There’s no guarantee here,” he said. “I am not claiming it is a sure shot — I am claiming it is the best shot.”