I am not a party activist, I'm just exploring my options. Was surprised to see one of the candidates in my constituency is from the SDP - I didn't know they still existed.
Researching I have found that: the original SDP disbanded in the 1980s when they merged with the Liberals to form the LibDems, but a few people didn't want the merger and re-formed the SDP a couple of years later.
The party seems to be growing. It was tiny for a couple of decades fielding only 2 candidates. 2 elections ago it was 6. Last election it was 20. This time it's up to 122. Still only about a fifth of constituencies.
Their policies are broadly left wing on economic principles and support for the poor and disadvantaged, with sensible non-koolaid stances on the issues that have driven a lot of us away from Labour, LibDems and Greens who might otherwise have got our votes.
I'm not 100% aligned with their policies, they are unfortunately a bit more pro-brexit than I would have liked and there's policies like e.g about prioritising married couples for social housing and limiting immigration that I disagree with.
They are clearly a small party that aren't going to win a much if anything but I am considering voting for them. My constituency is a very safe labour seat so I don't expect to make a difference but it seems potentially worthwhile to give the SDP some encouragement and see if they grow some more.