The most interesting, if not necessarily most probable theory of motivation for the release of the SCOTUS draft decision reversing Roe v.. Wade is pure politics. It goes something like this.
Having concluded the Court has the votes to overturn Roe in their decision on Mississippi’s new abortion law (Dobbs v. Jackson), and realizing the formal announcement is likely to come out in July only 4 months before the midterm election, someone conservative was concerned it would rile up pro-choice voters who would vote in record numbers. Better to get the outrage out of the way earlier, like ASAP.
Outrage is hard to maintain at a fever pitch, it lasts briefly and then burns out as, over time, the realities of life intrude. Getting the outrage over sooner, rather than later, is the reasoning behind this theory. It could be the motive for the leak.
