Very long winded article on why the democratic is marching leftward. Fish's observation is correct.
http://www.theatlantic.com/magazine/archive/2016/01/why-america-is-moving-left/419112/
With the Dean campaign came an intellectual revolution inside the Democratic Party. His insurgency helped propel Daily Kos, a group blog dedicated to stiffening the liberal spine. It energized the progressive activist group MoveOn. It also coincided with Paul Krugman’s emergence as America’s most influential liberal columnist and Jon Stewart’s emergence as America’s most influential liberal television personality. In 2003, MSNBC hired Keith Olbermann and soon became a passionately liberal network. In 2004, The New Republic apologized for having supported the Iraq War. In 2005, The Huffington Post was born as a liberal alternative to the Drudge Report. In 2006, Joe Lieberman, the Democratic Party’s most outspoken hawk, lost his Democratic Senate primary and became an Independent. In 2011, the Democratic Leadership Council—having lost its influence years earlier—closed its doors.
http://www.theatlantic.com/magazine/archive/2016/01/why-america-is-moving-left/419112/
With the Dean campaign came an intellectual revolution inside the Democratic Party. His insurgency helped propel Daily Kos, a group blog dedicated to stiffening the liberal spine. It energized the progressive activist group MoveOn. It also coincided with Paul Krugman’s emergence as America’s most influential liberal columnist and Jon Stewart’s emergence as America’s most influential liberal television personality. In 2003, MSNBC hired Keith Olbermann and soon became a passionately liberal network. In 2004, The New Republic apologized for having supported the Iraq War. In 2005, The Huffington Post was born as a liberal alternative to the Drudge Report. In 2006, Joe Lieberman, the Democratic Party’s most outspoken hawk, lost his Democratic Senate primary and became an Independent. In 2011, the Democratic Leadership Council—having lost its influence years earlier—closed its doors.