This dissertation investigates why some attempts at pacted transitions from non-democratic rule fail while others succeed. Using a mixed-methods design, the research determines the composition and characteristics of opposition organizations that enable pacting. The thesis draws on a data set compiled by the author comparing forty-five attempts at negotiations that resulted in three different outcomes: (1) an agreement was concluded, but one of the parties failed to comply with its provisions; (2) an agreement was concluded, and the parties followed through on the terms (successful negotiations), but it did not lead to democratization, and (3) an agreement was concluded, leading to democratization (a successful pact leading to democratization). The QCA analysis shows that almost always, only those negotiations that include an opposition with strong organizational capacity succeed and end up with democratization. In addition to the existing theoretical explanation that pacted transitions only happen in party regimes, my analysis shows that the strong organizational power of the opposition can be drawn from trade unions or the Church participating in negotiations, even if the initial regime is personalistic. All negotiations that included trade unions ended up with democracy. Likewise, all attempts at negotiations where the Church was present never failed, even if they did not always lead to democratization. The two paired comparisons using the most similar design approach show the two ways in which attempts at a pact can succeed (or fail). One path—shown by the paired comparison of the Tunisian and Egyptian revolutions during the Arab Spring) —indicates that the presence of a strong trade union can facilitate a successful pacted transition even when the rest of the opposition is poorly organized. The second path — exemplified through a paired comparison of the Ukrainian revolutions of 2004 and 2014 — indicates how the organizational capacity of the opposition movement can determine different outcomes even when the society and the interactions of actors are identical.