Based on the change of opinion after seeing a poster showing some of our country's problems (overpopulation/border control) I'd say "has" cracked rather than "is" cracked. The former describes an incident that caused an irrational change, the latter implies a long term defect. Farage, on the other hand, seems always to state the obvious situation but in an easily understandable way so one can only ever agree or spend time trying not to with subject changes, scare stories, or plain old denial.