WASHINGTON — The Senate on Wednesday voted to expand the economic stimulus package with a tax credit for homebuyers of up to $15,000, a provision championed by Republicans as addressing a root cause of the recession.

The tax break for homebuyers, which the Senate approved by voice vote without opposition, was the second amendment in two days intended to encourage consumers to make major purchases. On Tuesday, the Senate approved a tax incentive for car buyers, sponsored by Senator Barbara A. Mikulski, Democrat of Maryland, that would allow the deduction of sales tax and loan interest on purchases made this year.

The tax credit would give buyers 10 percent of the price of a primary residence bought within one year, up to $15,000, and is intended to stabilize plummeting home prices, which caused a wave of foreclosures and led to the near collapse of the financial system as Wall Street firms wrote down billions in mortgage-backed assets.