Hillary Clinton's White House hopes depend on the results from March 4 primaries.
"You know where i stand and you can count on me," Clinton said.
Of the four contests - Texas and Ohio are crucial. She's got to win at least one of them - another Obama sweep would be disastrous.
And she's sticking to her guns - hammering home her core message--that she's substance and he's all style; that she's got solutions, and he just gives speeches.
"Let's talk about what we're *actually* gonna do to translate rhetoric into reality and promises into plans."
Until recently, the race had been dominated by the economy, but Clinton has looked to sharpen the contrast between herself and Obama by jabbing her opponent on national security.
It's a charge Obama flatly dismisses, pointing to Clinton's vote for war as the ultimate proof of who's ready and who's not.
"We're still waiting to hear Senator Clinton tell us what precise foreign policy experience that she is claiming - that makes her prepared to answer that phone call at 3 o'clock in the morning," said Obama.
Without a strong showing tomorrow, the pressure will build on the Former First Lady to drop out. She got a hint of it yesterday from a former rival.
"I just think that D-day is Tuesday," said Gov. Bill Richardson of New Mexico. "We have to have a positive campaign after Tuesday. Whoever has the most delegates after Tuesday, a clear lead, should be, in my judgment, the nominee."
Both candidates will be spending most of their day in Texas. They've got events planned well into the night.