When Bill de Blasio takes the microphone on the Capitol steps Tuesday afternoon to unveil his progressive version of the Republican “Contract With America,” he’ll be continuing an odyssey that most people in politics find puzzling. Why is the mayor of New York, after less than a year-and-a-half on the job, jetting around the country to promote an agenda that has already been taken up by more experienced (Bernie Sanders) and more popular (Elizabeth Warren) national leaders of the left?

De Blasio isn’t even running for reelection yet, much less the presidency. And many of the ideas reportedly on his list—a higher minimum wage, free child care, higher taxes on the wealthy—are policies that he hasn’t himself been able to implement during his brief tenure at City Hall. Sure, de Blasio’s two ego-inflated predecessors, Rudy Giuliani and Mike Bloomberg, tried to take themselves national, but both former Big Apple mayors were well into their second terms and had longer lists of accomplishments to tout. The New York press, meanwhile, has been positively aghast at Hizzoner’s chutzpah. Commentaries and cartoons in recent weeks have highlighted how few people in Iowa knew who de Blasio was (“Most people think Bloomberg is mayor of New York,” one Democratic consultant told The New York Times); suggested the mayor has a big head and a comical misunderstanding of his own public image; and hinted that de Blasio was at risk of neglecting his duties at home by spending so much time away from the city.

The biggest news de Blasio has made during his national tour has been his refusal to endorse Hillary Clinton for president, despite having managed her first campaign for the Senate in New York 15 years ago. The mayor has said, not altogether unreasonably, that he wants to see Clinton’s “vision” for the country, after she spent six years outside of electoral politics. With big pushes on immigration and criminal-justice reform, Clinton has started to fill out her agenda. But on Tuesday, de Blasio will gift-wrap an entire campaign platform for the Democratic front-runner—should she choose to embrace it. De Blasio’s 13-point national agenda reportedly includes his signature achievement as mayor, a universal pre-kindergarten program, along with liberal favorites like paid family leave, a $15 minimum wage, higher taxes on the wealthy, union-friendly labor laws, opposition to unfair trade deals, and comprehensive immigration reform.

De Blasio’s program appears to be a condensed version of a 115-page report for the Roosevelt Institute from Nobel Prize-winning economist Joseph Stiglitz, “Rewriting the Rules of the American Economy,” which will be released earlier on Tuesday morning. The mayor will appear with Stiglitz and alongside Elizabeth Warren to unveil that proposal before leading a second event outside the Capitol in the afternoon.

In his report, Stiglitz dismisses a “minimalist approach” to tackling inequality in favor of a broad overhaul of regulations, spending programs, and tax laws.  “It would be easier, politically, to push for one or two policies on which we have consensus, but that approach would be insufficient to match the severity of the problems posed by rising inequality,” Stiglitz writes. He includes dozens of policy recommendations, and while many of them overlap with those from de Blasio and Warren, some go further. (Stiglitz calls, for example, for a Medicare-for-all policy on healthcare that most Democrats rejected in favor of the Affordable Care Act.) Among his proposals are a financial-transactions tax, a five-percent surcharge for the top one percent of income earners, new government backstops against bankruptcy and foreclosures, and raising the payroll-tax cap to fund an expansion of Social Security benefits.

De Blasio made stops in Iowa and Nebraska last month, and he plans a fund-raising trip to California after his visit to D.C. On Monday, he defended his travels on the grounds that his capacity to implement a progressive agenda is limited as mayor and that lobbying the federal government is an important part of his job. “I’ve got to use the tools we have here to address income inequality, and a host of other issues,” he told reporters. “But I also have to participate in changing the national debate and changing the reality in Washington in a way that will support the people of New York City. We’ve got to do both at once.” Yet while the Republican Congress is likely to ignore the mayor’s pleas, it was the divided legislature in Albany, along with Democratic Governor Andrew Cuomo, who blocked his push for higher taxes on the wealthy and an increase in the minimum wage.

It’s easy to read de Blasio’s aggressive national push and his reluctance to endorse Clinton in adversarial terms. The ambitious young mayor, snubbing his former boss, is trying to raise his political profile at her expense. But that’s probably not the case. For one, there’s little evidence that the Clinton campaign cares about what de Blasio is doing, or that she is offended by the absence of his embrace. Given the trajectory of Clinton’s career, it was obvious that she would face pressure from the left, if not a serious challenge for the Democratic nomination. And the charisma-starved rookie mayor is a much safer foil for Clinton than Warren, a household name who inspires real passion among progressives.

Judging by her initial policy statements, Clinton won’t find most of de Blasio’s agenda difficult to support, and she can do so without the appearance of begging for his backing. A chief talking point of Clinton’s early campaign is that she is determined to “earn” every vote. De Blasio, then, is not a kingmaker, but merely a stand-in for the type of progressive Democrat whose support Clinton is trying to lock down. He’s favorably disposed, and she’ll almost definitely get his vote. But she has to earn it, and on Tuesday, the New York mayor will show his former senator exactly how she can do so.