Known: They have successfully solicited donations from me for causes I consider critical, and their site says that the money they raise goes only to the specific causes for which it's solicited. E.g., I just got an email soliciting funds to fight the new indefinite detention law and implying that the funds would help finance a lawsuit brought by Chris Hedges et al. challenging the law.
Unknown: Their site says they raise money for Democrats (in general). Which nationally-known Dems have they raised money for? Is there any connection between this organization and the Democratic Party?
A lot of Progressive Organizations raise money on ActBlue for Progressive Candidates. I've donated through ActBlue for years. That doesn't mean all the candidates on there pages are as libreral as I might want. I feel safe donating to certain candidates on. their pages and also especially safe through various organizations that link to their pages. I always leave a tip.