WASHINGTON -- Sen. Rand Paul (R., Ky.) said Wednesday that he would oppose the budget measure Republicans are counting on to begin the process of repealing the Affordable Care Act, leaving the effort in danger of derailing if any other GOP senators defect.

The Senate on Wednesday took its first procedural vote on the budget measure, a vehicle that Republicans can use to repeal the 2010 health-care law with a simple majority vote. Republicans now hold only 52 seats in the Senate, where most legislation needs 60 votes to pass.