Dan Balz:

For months, Hillary Clinton successfully made the Democratic presidential race a test of who has the strength and experience to be president -- and watched her opponents struggle to keep pace. On Tuesday night, her rivals turned the tables on her, and for the first time in the campaign, Clinton could not pass the test.

Tuesday's debate in Philadelphia shifted the focus of the Democratic campaign from strength and experience to questions of trust and character. The result was the weakest performance Clinton has delivered in any debate this year and a rare instance in which her longer-term vulnerabilities were very much on display.