canuckseo - 5:40 pm on Dec 14, 2012 (gmt 0)
I think synoyms and related searches, especially where the number of competing sites is low, play a bigger part for those low competition searches. I've seen sites rank for phrases that they aren't optimized for simply because the page that ranks is similar to the search phrase. there is no anchor text pointing to that page for that phrase but there are other links on similar anchor text pointing to other pages on the site.
Freshness is a factor - i've seen sites i've freshly optimized rank highly for phrases. It depends on the site - a new site that is freshly optimized doesn't keep it's ranking as long while an older more established site has kept its rankings for new phrases merely on the optimization alone for some fairly competitive local terms. I haven't looked at backlinks for the older site but obviously because of its age it has links even if they are of the non-anchor text variety.
So while I personally think in general terms it is a mix of ocntent and links, the ratio of importance depends. IE in non-competitive searches links aren't as important. Pages can rank competitively on the optimization and content alone. With competitive searches links and content are equally important.
So what i'm saying is there is no hard and fast rule - sometimes links play a more important part in overall rankings and sometimes they do not.