Rather than the Texas two-step of earlier candidate debates, campaign watchers expect a shootout between the senators from Illinois and New York at the University of Texas in Austin as Clinton tries to mount a counter-offensive capable of upending the Obama juggernaut that has produced 10 straight state wins. The upcoming primaries in the Longhorn State and Ohio are expected to be pivotal, analysts told the Houston Chronicle.

"Debates can turn elections," said Ross Ramsey, editor of Texas Weekly, a non-partisan political journal. "A front-runner who stumbles can be overtaken, and a candidate who's trying to catch up -- or keep up -- can regain ground. A big moment by either candidate will get played over and over until everybody knows about it."

Clinton is known as a battle-tested debater and Obama the green-but-gifted orator.

"Overall, it's one of her strongest forums because it rewards the command of detail that she exhibits," Rutgers University communications professor David Greenberg said. "The stump speech plays more to (Obama's) strength."

A national audience was expected to tune in to watch them go at it, with the outcome not only of the March 4 primaries but perhaps the Democratic nomination, hanging in the balance.