The Congress has a legislative type of power, which it means that it has the power to make and propose new laws or amendments. However, the Congress can set time limits for ratification, even if this is not stated clearly in the Constitution. This practice began with the 18th Amendments, and after taht every amendment that has to be ratify has a deadline for the ratification.
Third-party candidates at the top of the ticket can help to draw attention to other party candidates down the ballot, helping them to win local or state office.