Read: O’Rourke mostly gets a pass for his lack of specifics

There are several different ways to address climate change through federal policy. O’Rourke’s plan tries to do all of them at once.

First, the government can try to make carbon pollution more expensive by regulating or taxing it. O’Rourke says that on his first day in office, he would reverse all of Trump’s climate-related orders, rejoin the Paris Agreement, and tell the Environmental Protection Agency to restrict air pollution from power plants and car tailpipes again.

He would also ask Congress to pass a “legally enforceable standard” that would force the United States to zero out its carbon emissions by 2050. What is this “standard”? Though the proposal’s language is cleverly vague, O’Rourke seems to be describing some kind of carbon tax—his exact language is “a clear price signal to the market”—that scales up as the mid-century deadline approaches.

Second, the government can try to make clean energy cheaper. O’Rourke says he will spend $200 billion on a new R&D program to study technologies that can reach his zero-carbon goal.

Finally, the government can buy things: solar panels, wind turbines, public transit, electric-car charging stations, and adaptations (such as seawalls) that will help people prepare for the worsened weather to come. O’Rourke says he would ask Congress to cut tax breaks for oil companies, using the resulting $1.5 trillion to fund new climate-ready infrastructure.

O’Rourke also promises to connect $500 billion in federal spending—spending that would happen anyway—to his climate goals. The federal government already tries to “buy American,” favoring U.S. companies and manufacturers; under O’Rourke’s plan, it would also “buy clean,” favoring steel, glass, and cement produced in a climate-friendly way. Some scholars associated with the Green New Deal have proposed similar new programs.

O’Rourke’s proposal goes much further than either Trump- or Obama-era policy. It will also face virtually guaranteed political opposition. But it combines a mix of approaches. Some of his proposals require new congressional legislation; some can happen through annual budget negotiations; some can be authorized by the president.

Take his proposed advanced-energy R&D program. The United States actually has an active energy R&D program, called ARPA-E, or the Advanced Research Projects Agency-Energy. Trump has proposed closing ARPA-E every year since he took office, but some Republicans and Democrats in Congress have resisted him. As such, ARPA-E now has a budget of $366 million—a record haul for the small agency.

But that all-time record is still 550 times smaller than O’Rourke’s $200 billion proposal. O’Rourke says that $200 billion is “an amount equal to what we invested in our nation’s journey to the Moon,” but I think that may actually understate the monetary scale of the proposal’s ambition: In inflation-adjusted dollars, $200 billion exceeds the cost of the 15-year Apollo program.