The former first lady's imposing national lead among Democratic voters faded leading up to the 22-state sweepstakes.
Two new books document Lincoln's difficult passage through the politics of race.
Some states have allowed primary votes to be cast as long as a month ago. In California, for example, up to half of all primary votes may be cast early.
Barack Obama launched ads for his campaign in New York this week, contesting Hillary Rodham Clinton in her home state.
A US-Iraq security pact won't set troop levels now, but it could set the stage for long-term strategy.
Comets and asteroids made of similar stuff, a bird needs more than plumage to pick a mate, and nanotech builds a better radio.
Steny Hoyer and Richard Durbin, key members of the Democratic congressional leadership, shared their views Tuesday.
Superdelegates, or party professionals, could play a decisive role in the outcome of the Democratic race.