1. Such putative loyalty will be tested by this session's bills, particularly broadcasting, legal reform and the NHS shake-up.
2. Despite such a poor start, he's subsequently risen to massive heights of fame, being second only to Cher in the showbiz hierarchy.
Both 'circumstances' seem identical to my uninitiated eye. Is there a governing rule? Is this an issue at all? Would replacing 'such a' with 'such' in the second sentence change its meaning and would the meaning of the first sentence be altered if "such' were replaced with 'such a'?
"Such" on its own for uncountable nouns (loyalty), "such a" for countable nouns (start). General rule!
I should point out that it only works for the context you quoted. It is, of course, perfectly acceptable to say things like "Such people are the problem with the world today" even though "people" are countable.
General rule (2) "Such" on its own for uncountable nouns (loyalty) and plural countable nouns (people) , "such a/an" for singular countable nouns (start).
Context is always important; labelling is rarely important.
I found both replies very instructive. Thank you.