Ask any political writer these days, and they'll give you a myriad of explanations of why Hilary Clinton's still in the race: She's setting herself up for 2012, she's invested so much she can't quit now, she's running out the clock hoping for a delegate face-off at the convention, blah, blah, blah.
Here's a new one to chew on:
She's setting herself up for a run as an independent in the fall.
Why not? Take a look back at history: In 1909, Teddy Roosevelt stepped down as President, and William Howard Taft stepped in. In 1912, Roosevelt ran again. When he lost the Republican nomination, he broke off, forming the Bull Moose party (officially, the United States Progressive Party of 1912), and ran against Taft. In the end, Taft and Roosevelt lost - to Woodrow Wilson.
Think history won't repeat itself? Think again. Considering that we've had three major independent candidates since 1980 (John Anderson and Ross Perot twice; four if you include Ralph Nader), there's no reason to think another independent candidate won't appear again.