While negotiators toiled late into the night in Switzerland, scratching together a nuclear agreement with Iran, Senator Bob Corker was conducting his own tense talks back home.
The new chairman of the Foreign Relations Committee, Mr. Corker, a Tennessee Republican, was trying to marshal a bipartisan coalition for his bill to force President Obama to send any agreement with Iran to Congress for approval — a bill that could get enough votes to overcome a veto by Mr. Obama.
“I know that the diplomats in Switzerland, knowing that Congress was likely to weigh in on this deal, that was a positive thing,” Mr. Corker said in a telephone interview on Monday. “Voting for this legislation will have a positive effect on the negotiations, not a negative effect.”
There are few people on Capitol Hill more important to the White House right now than Mr. Corker, the silver-haired senator with the Southern drawl who sees himself as a bridge builder in a Senate known for polarization. At the White House, nobody likes his bill, which would give Congress a 60-day window to debate the Iran agreement before voting yes or no or taking no action, but Mr. Obama and his advisers see him as someone who might work with them to revise the legislation and ultimately make a deal.
It is no surprise, then, that the White House has spent the last few days publicly stroking Mr. Corker.
“A good and decent man,” Mr. Obama declared.
“Somebody who has considered this issue in a very principled way,” said the president’s spokesman, Josh Earnest.
The White House now views its central challenge as either negotiating a compromise with Mr. Corker or stopping enough Democrats from joining him so that he is short of a veto-proof majority, at least through June 30, the deadline to translate last week’s preliminary agreement with Iran onto paper. After that, officials said, Mr. Obama may be in a stronger position to argue the merits of the accord.