The nomination of openly LGBT candidates is often seen in the US literature as a supply-side phenomenon. Namely, LGBT candidates will arise in those single-member districts whose population holds more favorable views toward the LGBT community. This approach overlooks the role of political parties actively recruiting minority candidates under some circumstances or hindering them in others. Moreover, it needs to consider how parties acting within proportional systems aim to produce balanced tickets to appeal to a broad group of voters. This paper introduces a new way to understand the nomination of LGBT candidates in such systems by combining the supply and demand sides. We propose that LGBT candidates will be more likely to appear in places with organized LGBT activism and be recruited by left-wing parties. Furthermore, we analyze the biographies of the nominated LGBT candidates to test the two mechanisms driving the previous relationships: increased tolerance and selective recruitment. We empirically assess these relations using a novel dataset on Spanish LGBT candidates and activist organizations.