Sen. Hillary Rodham Clinton (D-N.Y.) began laying the groundwork to battle on past the Texas and Ohio presidential contests Tuesday, even as supporters of her rival for the Democratic nomination said she should end her candidacy if she loses either state.

Clinton was reported on Monday morning as saying she’s “just getting warmed up,” and campaign officials have repeatedly spoken of Pennsylvania’s primary on April 22 as the next step.

Obama’s campaign manager, David Plouffe, responded on a dueling call that Penn himself has acknowledged that the race is for delegates. Even narrow wins in Texas and Ohio won’t be enough for Clinton to close the overall delegate gap between the two candidates, Plouffe said.

“They keep moving the goal posts, but at some point you run out of field,” Plouffe said.

Even former President Bill Clinton famously said the New York senator needs to win both Ohio and Texas to keep going.

Plouffe said Tuesday’s battles represent “the last big window of opportunity” for Clinton to close the delegate gap, but he expects to hear “more creative math and tortured explanations Wednesday morning.”

The Clinton campaign has shifted on its expectations for Texas and Ohio, but the conventional wisdom seems to have hardened that popular-vote wins in Texas and Ohio will provide Clinton with more than enough reason to stay in the race through Pennsylvania’s contest next month.

“I think it’s pretty clear if she wins two she goes on, if she loses two she doesn’t,” said Steve Elmendorf, a Democratic strategist and Clinton supporter. “If she splits them, there will be a lot of pressure to get out. Obviously it’s better to win both.”

The idea of splitting the states has not been explored as thoroughly, and Wolfson would say only that it’s “a fair question,” and if Clinton doesn’t win both states “we can discuss it then.”

But the pressure would undoubtedly intensify for Clinton to withdraw given that Republicans are beginning to rally around Sen. John McCain (Ariz.), who is enjoying a head start of sorts.

One Democratic strategist said that if Clinton splits the states, the situation would become “politically unsustainable.”

“I think the superdelegates will head for the hills,” the strategist said.

The Obama campaign said it “would never suggest what Sen. Clinton should do,” but Plouffe said at some point after Tuesday the Clinton campaign will “need to demonstrate state by state how they are going to reduce the delegate lead.”

By the Obama campaign’s math, there will be only 611 pledged delegates left to win after Tuesday, meaning Clinton would need to win 62 percent of the remaining delegates to catch Obama. The message from the Obama campaign is that narrow wins in Texas and Ohio will not help Clinton move closer in that column because of the Democrats’ method of allocating delegates proportionally by congressional district.

“It is a very simple question — what is their path to secure the nomination?” Plouffe wrote in a memo released by the Obama campaign. “No amount of spin can change the math. We look forward to their tortured answers on Wednesday morning.”

Over the weekend, two prominent Obama supporters, Sens. John Kerry (D-Mass.) and Dick Durbin (D-Ill.) offered a preview of the kind of pressure Clinton will likely face if she doesn’t win both states, suggesting she should withdraw in the absence of big victories.

“If you’re going to measure it by their own standards, then it’s very important to win; not just win but win big,” Kerry told reporters Monday.

Former candidate New Mexico Gov. Bill Richardson, who has not given an endorsement, said whoever has the most delegates after “D-Day” should be considered the winner.

The Clinton campaign appears to be looking for a reprieve Tuesday night that would give reporters more time to examine Obama.

An imbalance in media coverage has been a constant theme from the Clinton campaign, and has recently been parodied on late-night comedy shows.

With more concentrated criticisms of Obama on foreign policy and trade, and the trial of former Obama friend Tony Rezko starting Monday, Clinton campaign officials have repeatedly said they think Obama will wilt under the media glare that comes with front-runner status.

Penn and Wolfson said Monday that an ad Clinton started running Friday that calls Obama’s foreign policy experience into question has already resulted in a “tipping point and a change in momentum in the last week.”

For Clinton to reap any benefits from that intensifying glare, however, she has to win some breathing room Tuesday night.

Penn said Monday that while he won’t make any predictions, he doesn’t think there will be any “ambiguity” about whom the clear winner is Tuesday night.

“I believe it will be very clear Wednesday morning which campaign had the better of the day and which campaign had the worst of it,” Penn said.