U.S. president, mad as could be (5)

I believe the answer is:

adams

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'u s president' is the definition.
'adams' can be an answer for 'president' (I've seen this before). I am not sure about the 'u s' bit.

'mad as could be' is the wordplay.
'could be' is an anagram indicator.
'mad'+'as'='madas'
'madas' is an anagram of 'ADAMS'.

Can you help me to learn more?

(Other definitions for adams that I've seen before include "Gaolers" , "Richard --, Watership Down author" , "Former US president" , "Second and sixth US president" , "Of untidy appearance" .)

I've seen this clue in the Evening Standard.

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