Elizabeth Warren over Scott Brown
In this race Warren also have very few negative aspects (mostly minor) and many good aspects. The best of these being Uranus in-conjunct Chiron, Chiron conjunct Chiron, Uranus parallel Sun, Jupiter conjunct Uranus, Uranus contra-parallel Jupiter and Pluto parallel Jupiter.
Brown has some good aspects, especially Jupiter parallel Pluto, Uranus in-conjunct Pluto, Jupiter contra-parallel Ceres and Uranus contra-parallel Ceres. Unfortunately he also has Chiron opposition Pluto (twice), Ceres contra-parallel Saturn (twice) and Ceres contra-parallel Earth/Moon complex.
I believe these negative aspects will be hard to overcome especially as his opponent has very few negative aspects. Based on the above I'm picking Warren to defeat Brown.