In the US, reference ballotpedia.org -- search for your state and read through all information for candidates, as well as ballot initiatives (local news and MSM has failed at informing about initiatives). Active candidates may provide information, from survey results (Ballotpedia's questions) to providing links to public and private social media pages.

Somewhat fortunately, a lot of the third party candidates in my state this year are candidates I can support. I'm not optimistic about their chances of winning, but at least I can vote *for* someone and not against, thanks to doing some research.

Also, check out past candidate information on Ballotpedia. In one case, I'll be writing in a third-party candidate who has campaigned in previous elections, but is not running this year.