Former U.S. Secretary of State Hillary Clinton, the front-runner in the Democratic presidential-nomination race, could be outpaced by a competitor, according to the candidate herself. In a fundraising email sent Sunday morning, just hours after the Democratic debate Saturday night, Clinton asked potential contributors to donate to her campaign, warning she could lose the nomination.

"I don't know how else to say it except by saying it: We could lose the nomination," the email read. "The other candidates on that stage last night would like nothing more than for our team to sit back and relax right now, but I am not taking anything for granted. You can't either, I need your help."

The message said the campaign would "fight hard" to win the nomination and to continue on to the White House before requesting a $1 contribution. "I know you'll step up when I need you. Chip in $1 today," the email read.

Although Clinton may be saying she could lose the Democratic presidential nomination, she holds a significant lead in the polls over U.S. Sen. Bernie Sanders of Vermont and former Maryland Gov. Martin O'Malley. She leads nationally with 56.3 percent support, compared with Sanders at 30.6 percent and O'Malley at just 4.3 percent, according to the RealClearPolitics average of polls. While Sanders has appeared to do well in the early-voting states of Iowa and New Hampshire, recent polls have given Clinton about a 20-point lead nationally.

Clinton delivered a solid performance in the debate this weekend, with the Washington Post saying she "was the only one onstage Saturday night who looked like she could step into the presidency tomorrow." The New York Times noted that at times Clinton seemed to look past her Democratic competition in the debate at St. Anselm College in Manchester, New Hampshire, especially when she said Republican front-runner Donald Trump was "becoming ISIS's best recruiter," referring to the billionaire businessman's controversial remarks about Muslims immigrating to the U.S. and to the Islamic State group.