Definition of "cosponsor" [cosponsor]

• To function in the capacity of a joint sponsor of: corporations that cosponsored a marathon. (verb-transitive)
• A joint sponsor: two senators who were cosponsors of new legislation. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "In light of the way you cleverly parse other parts of your response "it COULD result in", "especially in regions where," etc. (emphasis mine), it's obvious that you are aware that the implication of calling someone a "cosponsor" of a piece of Senate legislation implies the joint cosponsor whose name is on the bill."
• "What we are upset about is that you ALSO can "cosponsor" legislation before and AFTER it is voted on."
• "Ask your U.S. representative to cosponsor this act when it is reintroduced."