In the Constitution, Congress was given the power of the purse-strings, so to speak, in that they control the budget of the Federal Government. While this makes good sense, they have also been given the power to raise their own salaries, which they have used many times through the years.
A group cannot be given the power to decide their own salary and not be expected to abuse it
Tax dollars pay this salary, and Tax Payers should decide it.
Lower the annual salary of Congressmen and Senators to just above the average cost of living in the United States, and have their pay raises put up to a vote by the General Public.
This will either drive down taxes or ensure that the money is being put to good use, and will also remove financial security from the motivations for taking office.