Biden still leads US Democratic primaries, Trump's ratings fall slightly after gun massacres, plus Australian preference flows
- Written by Adrian Beaumont, Honorary Associate, School of Mathematics and Statistics, University of Melbourne

After the first Democratic presidential debate on June 25-26, Joe Biden fell in Democratic national presidential polls, and Kamala Harris surged. In the lead-up to the July 30-31 debate, Biden recovered lost support while Harris lost some of her gains....