Why did the PNR (Portugal's Golden Dawn) fail to get traction at municipal elections?
As Hans said, they are a joke party. They aren't that similar to Golden Dawn - there were some neo-nazis and skinheads in the party a few years ago but they purged those guys: strictly from a popularity perspective, an ill-advised move as they actually had some access to the press in those times (surely not for the best reasons - but they're so irrelevant that no publicity is bad publicity and they actually went up to almost 20,000 votes). Nowadays they're more like a FN type of party.
It's hard to get traction when you're only running in 6 municipalities out of 308 - and I bet that in most of them they had to fill the list with carpetbaggers.
I actually disagree with Hans that this kind of parties have no hope of success in Portugal due to ideological reasons. Surely a proper fascist party, openly anti-democratic, etc, has no chance, but the reason a nationalist populist party doesn't do well are of different nature (as the MPT result in the Europeans prove to some extent - those votes belong to their frontrunner, Marinho e Pinto, an unabashed populist that made his name on daytime tv shows talking about society ills and not politics. Often ranting about conspiracies or introducing nativist themes).
- the main reason is that campaign finance laws make very difficult for new parties to surge. The four biggest parties in Portugal right now (and it's dubious the BE is still a major party) are the same four biggest parties that existed in the first democratic elections. Public financing is allocated by incumbents - just like press coverage tends to be allocated by the same criteria.
The only exceptions to the big 4 dominance were the PRD (curiously the same party that is now the PNR - they took over the PRD corpse instead of creating a new party), which was a personalist party build around former PR Ramalho Eanes. As soon as Eanes left active politics, the party folded; and the BE that benefited from being very popular among the journalist class (due to their focus on some social issues) and a charismatic leader - but they've been on a steady decline since Louçã left.
- the far-left has the protest vote market cornered. A party of that kind would need to conquer votes from the PCP (and to a lesser extent the BE) but by refusing to assume government responsibilities, the PCP keeps attracting those votes.
- immigration isn't an issue in Portugal. There aren't enough immigrants to make it one (and in the last view years there was net emigration) and those that exist are mostly from the former colonies, so pretty close in terms of language/culture plus some from Easter Europe, especially Ukraine, who've stayed despite the crisis and tend to be well-regarded/assimilated. There is no meaningful religious minority and the minority/crime association results completely hollow in most of the country.
In the end, a large majority of the Portuguese doesn't really know what the PNR is or what they stand for. Which is true for almost all minor parties, except maybe the PCTP/MRPP.