Liberal groups say Hillary Clinton is a blank slate when it comes to certain policies and are pressing her to side with them on the Keystone XL pipeline, deportations, financial regulation and other matters.

The push for Mrs. Clinton to flesh out her views comes as she has stepped up her public appearances ahead of a likely campaign for the 2016 Democratic presidential nomination. She has addressed college audiences in recent months, said goodbye to TV personality Barbara Walters on the set of the "The View," and...