Short forms for US political parties

Both the main parties have longish names ? yet no short forms have been established, appropriate for regular use in contexts of middling formality ? news articles in the ?Washington Post', for instance.

For the Republicans, one has ?GOP' ? which is useful for a touch of ?elegant variation' in certain usages: one can use the acronym instead of ?Republican' in the sentence
?Sen Bill Frist is a Republican senator';
but not in
?Sen Bill Frist is a Republican' (?Sen Bill Frist is GOP' is not, I think, an exact equivalent).
But it doesn't feel right to use GOP as the standard (or should that be, ?regular'?) short form for ?Republican'.
There seems no equivalent of GOP for the Democrats. I see ?Dems' used to describe persons, but get the impression this is a recent development ? Mr Webster (1) does not date the abbreviation. He does allow it for both Democrat and Democratic ? I have the feeling that it is used much less in this latter function than GOP: would one refer to ?Dem policies' as easily as ?GOP policies'?
(The strange twins ?Democrat(ic)' have been discussed more than once here, I see.)
(In Britain, the standard names of the main parties are Conservative and Labour; use of the alternative ?Tory' (for Conservative) is, I think much freer than of GOP for Republican. There is no alternative name for Labour ? the Tories used to call them ?Socialists' as a term of abuse, but then, along came Blair
In Continental Europe, parties generally have names of several words, which are expected to be referred to by their initials in all but the most formal of contexts; in Spain, one rarely sees the left wing Partido Socialista Obrero Español referred to as anything other than PSOE; the various incarnations of the Gaullist party in France were always referred to by their initials, except by ignorant foreign journos, tempted to show off their language skills with a ?surtraduction' of the full name!)
(1) http://m-w.com/cgi-bin/dictionary?book=Dictionary&va=dem