President Donald Trump’s decision to approve the foreign sale of U.S. Steel, an American manufacturing icon, came after months of sustained pressure from a group of Rust Belt Republicans.

Advocates for the deal say the lobbying effort was crucial to the president’s reversal of his campaign pledge to block the nearly $15 billion sale, which he will formalize in a speech at the company’s Pittsburgh headquarters on Friday.

“That should have been a no-brainer, frankly, and lawmakers in Trump’s corner helped him see that,” said one former Republican official, who is in favor of the deal and familiar with the discussions at the White House.