Huffington Post: The fragile but growing congressional effort to bring oversight to ongoing nuclear negotiations with Iran is at risk of unravelling, as lawmakers from both sides push for controversial additions to the bill.

On Tuesday, Senate Foreign Relations Committee Chairman Bob Corker (R-Tenn.) will formally introduce legislation for markup that would grant Congress the final vote on any nuclear deal and prohibit the president from waiving economic sanctions against Iran for two months while lawmakers review the terms of the agreement.

In the days preceding the markup, senators from both parties have introduced a slew of amendments, with several Democrats seeking to strike the more contentious clauses and Republicans vying to add even more restrictive language. The addition of any one of these could convince some of the more reluctant co-sponsors to abandon ship — giving President Barack Obama the margin he needs to ensure that his veto is not overridden.