GUATEMALA CITY (Reuters) - A comic actor rode a wave of outrage over corruption to win the most votes in Guatemala's presidential election on Sunday and is seen as having a strong chance of winning a runoff next month.

Jimmy Morales, 46, who is new to politics and campaigned under the slogan "not corrupt, not a thief," has promised a transparent government if he wins the presidency in a second round vote on Oct. 25.

It remains unclear if he will face a former first lady or conservative businessman, who are still fighting for second-place finish in Sunday's vote.

After the massive corruption scandal that forced former President Otto Perez to resign last week, analysts say Morales could hold a big advantage over either opponent in the runoff, however. As an outsider he is seen as unblemished by a discredited political system.

"I believe Morales will win in the second round, irrespective of who joins him," said Gavin Strong, a Central America analyst at consultancy Control Risks.

As votes trickled in on Monday, Morales had 23.92 percent support with 97.86 percent of polling stations counted. That was far short of the 50 percent needed for an outright victory, but he was still comfortably ahead of his rivals.

Sandra Torres, the ex-wife of former President Alvaro Colom, had 19.62 percent of the votes, just ahead of conservative businessman Manuel Baldizon with 19.60 percent.

Until recently, Baldizon had been favored to win.

Strong said he thought Morales would win next month because both Torres and Baldizon would likely back the comedian if either of them failed to progress.

Consultancy Eurasia Group also predicted a likely second-round win for Morales. "While the second round will be tight, Morales will probably win because most of the smaller parties are conservative and will support him," the group said.

Morales played on his humble roots selling bananas and used clothes on the streets as a youth, and wooed crowds with jokes and references to a TV show he produced and starred in with his brother Sammy called "Moralejas" or "Morals," in which the pair dressed up as spies and mafia hoods in comedy sketches.

"My program in a nutshell: complete openness," Morales said as his place in the runoff was assured, vowing to propose forming a constitutional assembly alongside the country's discredited Congress if he wins the run-off.

Critics say Morales' party is controlled by right-wing military figures. He denies that and defines himself as a centrist who would fight poverty by improving education and decentralize the budget and government powers.

His plan includes giving out smartphones to children and tackling corruption.

Morales also described Guatemala's current 1 percent royalty on mining production as "robbery", at a news conference on Monday. While he would not name a level he supported, he said that 5 to 10 percent was "low."

Baldizon's campaign was tainted by a separate graft scandal, when his vice presidential running mate, Edgar Barquin, a former central bank chief, was accused of criminal association and influence trafficking by a powerful United Nations-backed anti-graft commission. Barquin has not been charged.

Even if Morales wins, Strong thought it unlikely he would be the driver of any significant change as president.

"Pervasive corruption will remain one of the principal obstacles to doing business in Guatemala when the new government takes office, irrespective of who's president," he said.

Perez resigned as president on Thursday and he spent election day in jail while a judge considered charging him over a customs corruption racket that plunged the country into its worst political crisis in two decades.

Congress has sworn in Perez' vice president, Alejandro Maldonado, to fill out his term until power is handed over to the eventual winner in January.

Guatemala is Central America's largest economy and the next president inherits a poverty rate that remains stubbornly high despite nearly uninterrupted economic growth since the end of a 1960-96 civil war.