But Clinton advisers have recently pointed to Mr. Obama’s financial advantage, in what appears to be an attempt to lay the groundwork to stay in the race should she lose by a small margin or squeak to victory in either or both states. “They are dumping a lot of money there,” said Mrs. Clinton’s chief strategist, Mark Penn, referring to the Obama campaign.

That said, Mrs. Clinton once enjoyed double-digit leads in both states, and her campaign had told supporters concerned about her string of losses that her effort to win the Democratic nomination would get back on track after solid wins in Ohio and Texas. Democrats said narrow victories there might not be enough to stanch a flow of uncommitted superdelegates  elected officials and party leaders  to Mr. Obama, who have until now deferred to the request by Mrs. Clinton’s advisers to wait for the vote in the two states.

Mr. Obama, campaign officials said, has spent about $10 million on television advertising in Texas since early February; Mrs. Clinton has spent just less than $5 million. Mr. Obama has spent about $5.3 million for television advertising in Ohio, compared with just under $3 million for Mrs. Clinton, the officials said.

Those figures do not take into account substantial advertising being presented for Mr. Obama by the Service Employees International Union. It also does not include money that Mr. Obama and Mrs. Clinton spent in Texas on Spanish-language television and radio stations in a competition for Latino voters, whom Mrs. Clinton had once considered an unassailable part of her base.

“I have many friends in Texas; I know your tradition and culture,” Mrs. Clinton said in one commercial broadcasting in Houston this weekend, speaking into the camera as subtitles translate her remarks into Spanish.

Mr. Obama’s financial advantage is helping him beyond the airwaves. His campaign flew 200 paid organizers from across the country to 10 campaign offices in Texas right after the Feb. 5 primaries, aides said, when some of Mrs. Clinton’s staff members were volunteering to work without pay. Another 150 were sent to build get-out-the-vote networks in Ohio, working for Paul Tewes, who was the Obama campaign’s director in Iowa. Mr. Obama’s eight-point victory in that state’s caucuses gave his campaign a huge boost.

Mrs. Clinton’s on-the-ground effort is no less aggressive and extensive; in particular, she has tapped into the network of support provided to her by Mr. Strickland. But in both states, her corps of workers are made up largely of volunteers. Many are from the two states, but others came here and to Texas on their own dime  typically from Washington and New York, some responding to an e-mail plea from Chelsea Clinton.