By Zach Dyer
SAN JOSE, April 3 (Reuters) - Costa Rica's center-left presidential candidate Luis Guillermo Solis is expected to cruise to victory in Sunday's run-off election after his ruling party rival quit campaigning in a bizarre twist last month.
Solis surprised pollsters by coming in ahead of Johnny Araya of the ruling National Liberation Party (PLN) and the other candidates in the first round of voting in February.
Although he fell short of the 40 percent support needed to avoid a runoff, he then took a strong lead in opinion polls by channeling resentment over rising inequality and government scandals that have rocked the coffee-producing nation.
Araya was stunned by his fall in the polls and last month abandoned the campaign, setting the stage for Solis' Citizen Action Party (PAC) to win the presidency for the first time.
"From 1949 to the present, nothing like this has ever happened," said Jose Carlos Chinchilla, a political analyst and a director at the University of Costa Rica, predicting a resounding win for Solis. "The desire for change is absolute."
The constitution requires that Araya remain on the ballot and his party continues to campaign so theoretically he could win, but many voters are eager to toss out President Laura Chinchilla's scandal-ridden ruling party and Araya's withdrawal from public events further boosted Solis' chances.
An academic and former diplomat who has never before been elected to office, Solis has pledged to improve infrastructure, overhaul health care and stamp out corruption.
Araya, a former governor of San Jose, lost ground with voters over a series of gaffes during the campaign, such as underestimating the price of milk in an interview.
A prosecutor's probe into allegations of abuse of authority and embezzlement while Araya was mayor of San Jose also dampened his appeal.
"I am going to vote against Johnny Araya!" said Manuel Gerardo Ortiz, 66, a retired truck driver. "I used to be a Liberation Party supporter, but there was a lot of corruption."
A University of Costa Rica survey last month showed Solis had more than 64 percent support with Araya trailing on around 21 percent. Within hours, Araya said he would no longer campaign.
If elected President, Solis will face a divided Congress and grapple with growing government debt that totals more than half of Costa Rica's gross domestic product.
Moody's Investors Service, which rates Costa Rica a cut above speculative grade, revised its outlook for the country to negative from stable in September, citing fiscal concerns.
Solis, 55, has said he will not present fiscal reforms aimed at boosting tax receipts for two years if he wins but he told Reuters he would lay the groundwork by combating tax evasion, government waste and contraband.
"If there is anybody from the PAC who has an ability to make alliances and make deals across parties, it's Solis," said Michael Shifter, President of the Inter-American Dialogue.
Solis also has said he hopes to attract new businesses to set up shop in Costa Rica's booming free-trade zones, which have enticed the likes of Intel Corp and Hewlett Packard . (Writing and additional reporting by Alexandra Alper; Editing by Simon Gardner and Kieran Murray)