SYDNEY, Australia — Australia’s hankering for a United States ambassador hit another snag on Tuesday when Senator Bob Corker of Tennessee announced that he had turned down the job.

“At the end of the day, I just felt like it wasn’t the right fit and I still had work to do in the Senate,” Senator Corker, a Republican, told Reuters.

Talk about rejection. It was the second “no, not me” in less than a month. In April, President Trump withdrew the nomination of Adm. Harry B. Harris, the head of the Pacific Command, assigning him instead to South Korea.

Australians have been reeling ever since.

Why? From Australia’s perspective, this isn’t the first offense. And Australia is not just any ally.