Why is the 2016 Democratic field so old?

The Washington Examiner reports:

Why are the Democrats running for president so old? Blame the Clintons.

There are five Democrats who have either declared or are thinking about running for president. Three — Joe Biden, Bernard Sanders, and Jim Webb — will be over 70 years old on Inauguration Day 2017. Frontrunner Hillary Clinton will be nine months short of 70. Only Martin O'Malley, who will turn 54 a couple of days before the 2017 swearing-in, has not reached retirement age already.

In 2008, Democrats had a 47 year-old candidate who mesmerized the party and ran away with the votes of Americans aged 18 to 29. Republicans, meanwhile, ran a 72 year-old man whose reputation was based on heroism in a war 40 years earlier. Youth won.

In fairness, Barack Obama's ObamaCare law ended many Democrat careers.