a Member of Congress who joins with the sponsor in originally introducing the legislation, or officially supporting it after the measure has been formally introduced to the Congress

a Sponsor (single or joint) whose income is included in the sponsoring of an alien

The sponsor(s) of a bill or resolution in addition to the prime sponsor.

One or more persons proposing any bill or resolution.

Any member signed on, other than the prime sponsor, proposing any bill, joint resolution, or resolution. Each bill/joint resolution/resolution has a prime sponsor and co-sponsors.

The legislator introducing a bill is known as the prime sponsor. Those who "sign on” afterwards are known as co-sponsors.

A sponsor of a bill or resolution who is not the principal sponsor.

To formally include a legislator's name on the list of a bill's or amendment's introducers.

A senator or representative who joins in sponsoring a piece of legislation but is not the one who introduced the legislation. A large number of co-sponsors increases a bill’s chances for consideration.

A member or members that add his or her name formally in support of another members bill. In the House a member can become a co-sponsor of a bill at any point up to the time the last authorized committee considers it. In the Senate a member can become a co-sponsor of a bill anytime before the vote takes place on the bill. However, a co-sponsor is not required and therefore, not every bill has a co-sponsor or co-sponsors.