1
general::
Also, if worse comes to worst. In the least favorable situation, if the worst possible outcome occurs. For example, If worst comes to worst and the budget is not approved, the government will shut down, or Go ahead and go to school with a cold; if worse comes to worst the teacher will send you home. This expression is nearly always followed by a solution. [Late 1500s]
American Heritage Idioms
2
general::
Phrase(s): if (the) worst comes to (the) worst
Prov. in the worst possible circumstances; if the worst possible thing should happen. • We should be able to catch the four-thirty train, but if the worst comes to the worst, we could get a taxi and still get into town on time. • Of course, I hope that your wife’s health recovers, but if worst comes to worst, I want you to know that we’d be happy to have you stay with us.
McGrawhill's American Idioms And Phrasal Verbs