With a record defeat on her Brexit deal, and a no confidence vote looming, the question must now be asked, should the Prime Minister of the United Kingdom, Theresa May, resign, before such a no-confidence vote, that she may lose?
I believe she should, as it might be the only way to save the office of Prime Minister for the Conservatives in the short term (nothing, short of a major scandal by Corbyn or the next Labor leader, is really going to stop Labor from winning at the next election the way things are going, however).
Corbyn IS a major scandal.
Regardless, she should leave if the polls indicate another candidate can do significantly better. But any leader is going to find themselves in this fix unless they commit to a revote.