“You know I made it very clear that this election is about all of you,” she said at a morning rally on a chilly street corner in Dallas Friday morning. “It’s about your futures, your families, your jobs.”

“For me,” she added a moment later, “it really is about what we can do together.”

Her opponent, Mr. Obama, spent Friday campaigning in parts of southern and central Texas, targeting areas that are home to many Hispanic voters, who are seen as potentially decisive in the March 4 Texas primary. His first appearance was at the University of Texas-Pan American Friday, his first in the strongly Democratic Rio Grande Valley, where Hillary Clinton has a long history of support. After that, he planned to hold rallies in Corpus Christi and Austin.

In an interview on the CBS “Early Show,” Mrs. Clinton was asked directly if her closing debate remarks meant she thought she was going to lose the race. Mr. Obama has won 11 straight contests since the Super Tuesday races on Feb. 5, all by double-digit margins.

“No, of course not,” she said. “It is the recognition that both of us are on the brink of historic change. You know, I’m very proud that we have the two of us in this contest seeking the Democratic nomination, hoping to become our next president. Obviously, I believe that, you know, my record and my plans for what we can do for our country are ones that, you know, really are rooted in my experience and my strengths, being able to bring about the positive differences that people talk to me about.”

Her appearance in Dallas was marred by the death of the city police motorcyclist killed in a crash while escorting her motorcade. The crash occurred as Mrs. Clinton was being driven from the airport to a rally in the city. The officer was at the head of the line of vehicles. Dallas television station WFAA reported that the motorcycle may have struck a concrete abutment.