As crunch time nears for an Iran nuclear deal, Washington heavyweights are piling on the pressure.
Bob Corker, the Republican Senator who has led the charge for Congressional oversight, has written to the president, warning against the erosion of red lines.
Five of Barack Obama’s top former Iran advisors have signed an open letter expressing concern that the deal might lack sufficient safeguards to deter Iran from building a nuclear bomb.
And the administration has intensified briefings with lawmakers amid a series of media leaks suggesting concessions in the negotiations.
These interventions add to the challenge of the end game, and raise questions about the sustainability and credibility of whatever it might produce.