She has been compared to U.S. Sen. Hillary Rodham Clinton, who like her is a lawyer and senator who soldiered alongside a husband as he rose from small-state governor to his nation's presidency.

At Fernandez's campaign headquarters, supporters jumped up and down and embraced one another.

"I'm so excited," screamed Maria Isabel Francia, a 50-year-old street merchant. "Cristina is going to pull us out of poverty!"

Her challengers were trying to force her into a November 25 runoff. She needed 40 percent of the vote, with a lead of more than 10 percent over her nearest rival, to win outright.