One Republican fled Baltimore rally at fault (2,5)

I believe the answer is:

to blame

I'm a little stuck... Click here to teach me more about this clue!

'at fault' is the definition.

'one republican fled baltimore rally' is the wordplay.
I cannot quite understand how this works, but
'one' could be 'me' (a setter might use 'one' to humourously mean 'me') and 'me' is found in the answer.
This may be the basis of clue (or it may be nonsense).

Can you help me to learn more?

I've seen this clue in the Sydney Morning Herald.

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