A key Senate leader appears to be leaning toward proposing a new tax on employer-provided insurance benefits and creating a new federal agency modeled on one in Massachusetts to make it easier for individuals and small groups to buy insurance. The Senate Finance Committee is discussing a series of policy options for sweeping healthcare legislation. The committee released options for insuring the nation's 47 million uninsured, including expanding Medicaid, subsidizing private insurance for low-income people, and creating a public insurance plan.