The Clinton campaign said it was deploying staff members from other states to Ohio and opening offices in every Congressional district. In Texas, it has opened 20 offices and enlisted 4,000 precinct captains, almost halfway to where it wants to be, campaign officials said.
Texas’ byzantine delegate-selection rules pose a particular challenge to the Clinton forces. Districts that produced heavy Democratic majorities in past contests get a disproportionate share of the delegates, and this favors Mr. Obama because of large turnout in 2004 and 2006 in college towns and black precincts, where he has done well in other states. Mrs. Clinton’s strength is in the cities along the Mexican border, where she is popular with Hispanic voters, but which produce fewer delegates.
Adding to the complexity, Texas holds a primary and a caucus on the same day, with the evening caucus open only to those who have already cast primary ballots, either in early voting (which began Tuesday) or at the polls on March 4. Mr. Obama has prevailed in most caucuses up to now.
Mrs. Clinton said she could not begin to explain how the Texas system worked. “I had no idea how bizarre it is,” she said aboard her plane flying from Wisconsin to Ohio. “We have grown men crying over it.”
Clinton campaign officials have admitted being ill prepared for the series of contests after Feb. 5. Further evidence came this week when The Philadelphia Daily News reported that the Clinton campaign in Pennsylvania had failed to file a complete slate of delegates for that state’s primary, falling 10 or 11 delegates short of the 103 delegates to be elected at the district level. Under party rules, however, those delegates could be restored later. Phil Singer, a campaign spokesman, said, “We expect every one of our slots to be filled after the Pennsylvania primary.”
After winning 23 contests before Tuesday, the Obama campaign is intensely competing in Texas and Ohio. Television advertisements started running in both states last week, including Spanish-language advertisements in Texas.
In Ohio, two advertisements focus on the state’s battered economy and promise job-creation programs and an end to corporate tax loopholes; another is biographical, and a fourth paints Mrs. Clinton as an embodiment of the past.
The Obama campaign has opened 10 regional offices in Texas, aides said, and plans to open more before the primary.
Their strategy for Texas, Obama aides said, includes appealing to African-Americans in Dallas and Houston, as well as building upon the senator’s popularity in Austin, where a rally last year drew 20,000 people. But Mr. Obama’s first appearance in the state on Tuesday, in the heart of a Hispanic neighborhood in San Antonio, underscored his effort to compete with Mrs. Clinton for Hispanic supporters.
Adrian Saenz, the Texas director of the Obama campaign, said 125,000 volunteers in the state had signed up to help the campaign when the operation formally began three weeks ago.
“We’re not giving up any part of the state, regardless of where folks may say the Clintons have deep roots,” Mr. Saenz said in an interview, adding that the campaign intended to find support among younger Hispanic voters. In the fight for Ohio, Mr. Obama has dispatched his top operatives, including Paul Tewes, the Iowa campaign manager, to run the state effort. Teams of organizers from states that held contests on Feb. 5 have also been dispatched to Ohio and Texas.
The Clinton campaign plans to spend millions of dollars on advertisements in the two states, with an emphasis on Mrs. Clinton’s experience and her economic message, which has taken on a new populist tone in recent days.
A new television advertisement in Ohio, “Night Shift,” is directed at lower-income voters, who have formed a bulwark of her support so far. It speaks of those who clean up in hair salons, work late at diners and pull the overnight shift in hospitals.
The Clinton campaign says it has raised $15 million in 15 days this month, most of it from online contributors, and top aides say they will be able to match Mr. Obama’s spending in the coming contests.
“We’re going to run a campaign down here in which we concede absolutely nothing,” said Ace Smith, the Clinton campaign’s Texas director and director of Mrs. Clinton’s winning campaign in California.
John M. Broder reported from Parma, and Jeff Zeleny from San Antonio. Mary Ann Giordano and Dalia Sussman contributed reporting.