"What worries me is that [the FMLN] wants to change the system: nationalize businesses, take over private businesses," said Hugo Barrera, a businessman who co-founded Arena during the early 1980s. "They have been saying that for 16 years."
But many on the left say Funes' candidacy is itself evidence of how much the FMLN has changed since combatants traded guns for positions in the Salvadoran government.
"Mauricio is an expression of the transition," said Gerson Martinez, a one-time FMLN fighter who is now a lawmaker.
Funes' best electoral ally may be the growing anger over continuing price hikes for basic food items and gasoline. Discontent rippled through the crowd in El Paraiso, traditionally a conservative bastion.
Farmers complained of soaring fertilizer prices. Others cited a shortage of work. Many spoke fervently of the need for change but did not have specific remedies in mind.
Maria Teresa Tobar, 58, who is raising an 11-year-old daughter alone, said she is considering voting for the FMLN for the first time because she cannot make ends meet on earnings from a small plot of corn and occasional work ironing clothes.
Tobar said Arena governments had abandoned her, though she sent two sons to fight for the army during the war. One lost an eye in battle and the other later moved to the United States.
"I don't trust the FMLN, but I feel alone," Tobar said, standing at the edge of the Funes rally. "I gave my two sons to the government, and now I have nothing."