Senate Democrats announced a 15% minimum tax on large companies’ income on Tuesday, winning support from a key moderate lawmaker, as they try to generate enough money to pay for President Biden’s social-spending and climate-change agenda.

Sen. Kyrsten Sinema (D., Ariz.) endorsed the proposal, after balking at other forms of tax increases. Her objections in the evenly divided Senate have sent lawmakers searching for alternatives in an attempt to cobble together money to cover nearly $2 trillion in spending over a decade.

The business tax proposal is “a commonsense step toward ensuring that highly profitable corporations—which sometimes can avoid the current corporate tax rate—pay a reasonable minimum corporate tax on their profits,” Ms. Sinema said. The White House also backed the plan on Tuesday…

The corporate minimum tax plan, which resurfaces an earlier proposal from Mr. Biden, would affect about 200 companies and could raise hundreds of billions of dollars according to its sponsors, Sens. Elizabeth Warren (D., Mass.), Angus King (I., Maine) and Ron Wyden (D., Ore.).