In 2003, Dan Sullivan, then a White House national-security staffer, was in the Oval Office when China’s vice premier promised President George W. Bush the country would fix intellectual property theft. It didn’t.

In 2015, Mr. Sullivan, now a freshman Republican senator from Alaska, watched Chinese President Xi Jinping promise President Obama that China wouldn’t steal trade secrets through cyberhacking or militarize the South China Sea. “Has China kept these commitments? No,” Mr. Sullivan declared on the Senate floor earlier...