Taking advantage of his financial edge, Senator Barack Obama is buying large amounts of advertising and building extensive get-out-the-vote operations in an effort to end Senator Hillary Rodham Clinton's candidacy with twin defeats Tuesday in Ohio and Texas.
The intensity of Mr. Obama's drive is especially apparent on television, where he has outspent Mrs. Clinton by nearly two to one in the two states. That is helping him eat deeply into double-digit leads she held in polls just weeks ago.
But after a month in which she raised $32 million -- a remarkable amount, but still less than the $50 million or more brought in by Mr. Obama -- Mrs. Clinton is fighting back.
Their expenditures, combined with a travel schedule that sent the two Democratic presidential candidates and their surrogates from border to border in Texas and Ohio, reflect the expectation that the voting this week may be climactic. Mrs. Clinton's advisers have suggested that she will bow out of the race if she falters in either state, after 11 straight losses.
Their face-offs are not just on television. Mr. Obama, of Illinois, has a town-hall-style meeting Sunday afternoon in Westerville, Ohio. Mrs. Clinton, of New York, just announced one there, too. Mr. Obama will be at Westerville Central High School, Mrs. Clinton at Westerville North High School.
Polls show the race deadlocked in Texas. Mrs. Clinton's lead in Ohio has been whittled away, though she does still lead.
"Senator Obama is spending a lot of money on TV. If this can be purchased, he can win it," Gov. Ted Strickland of Ohio, who has campaigned across the state with Mrs. Clinton, said in an interview. "I think we've survived the initial blast of the Obama phenomenon, and we're now holding steady."
In a sign of Mr. Obama's confidence and his strategy of amassing delegates wherever he can, he spent part of Saturday in Rhode Island, which with Vermont also votes on Tuesday.
Aides to Mrs. Clinton said she remained confident of winning the Ohio and Texas contests and would press on with her campaign, as signaled by her increasingly tough attacks on Mr. Obama.
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 by a few votes 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.