For Aquarius Ascendant, there is a need to be socially significant, through the expression of individuality. Having a Leo Descendant suggests that personal significance is often experienced in the realm of relationships with others, and dealing with the public.
Uranus’ (ruler of Aquarius) position in the natal chart, through house placement, rulership, aspects etc, will suggest how/where the expression of individuality can be most expected:
In Obama’s horoscope Uranus is in the 7th house (the public), and contacts the Midheaven (career). This suggests “public career”, and the fact that Uranus is unaspected by other planets (called “peregrine” by Noel Tyl) makes its expression even stronger.
Actor Shia La Beouf has Uranus in 10th house, aspecting Sun (ruler of 7th) and Jupiter (ruler of the Midheaven) – a social significance attained through magnified, individualistic career expression.
Interestingly, Karl Marx also has Uranus in the 10th, but aspecting Saturn and Pluto (ruler of 9th) – which corroborates the social significance he attained through serious academic expression.
The individuation need is great for people born with Aquarius Ascendant, probably because of the intense social awareness that comes with this placement: for them, other people’s individuality and social significance are recognized so vividly that it becomes imperative to become (at least) as interesting as the people around them.