Republicans and many Democrats were already skeptical of a long-awaited nuclear agreement with Iran when they got word last week that the accord included two "side deals" that had not been seen by anyone in Congress.
The news has left Republicans more determined than ever to block the agreement, formally knows as the Joint Comprehensive Plan of Action, and has given undecided lawmakers more reason to doubt the accord.
Congress has begun a 60 day review period, after which they will vote on whether to approve or disapprove of the nuclear deal.
"Unless Congress gets the content of these agreements," Sen. Tom Cotton, R-Ark. said during an interview on MSNBC last week, "I don't see how anyone in Congress can vote for this deal because it is based on verification and inspection, and without that information I don't see how we can trust the government of Iran."