"Then Theresa May does have form for appointing people with no obvious credentials to big jobs."
(The Guardian.)
Does does have form for appointing... mean "to have and enjoy a notoriety for being prone to appoint people with no obvious credentials to big jobs" in the sentence above?
Correct, it means she has a reputation / track record of doing so.
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I interpret this as: "May has continually appointed people with no obvious credentials to big jobs. So the speaker is being sarcastic here, saying she does this so often she might as well have a (the article is apparently dropped in British usage) standard form for it."