Factbox: Uruguay's presidential candidates and their policies

By Malena Castaldi and Esteban Farat MONTEVIDEO (Reuters) - Uruguayans began voting on Sunday in the first round of a presidential election, with opposition challenger Luis Lacalle Pou almost certain to force leftist ruling coalition candidate Tabare Vazquez to a run-off. Vazquez, 74, who was president from 2005-2010, is polling at around 43 percent, short of the absolute majority required to win outright in the first round. Opinion polls taken ahead of the vote showed Lacalle Pou of the centrist National Party winning about 31 percent of votes in the first round and the two men running neck-and-neck in a runoff next month. Below are the two main candidates and their policies. TABARE VAZQUEZ, RULING "BROAD FRONT" In his first term as president, Vazquez pursued a center-left agenda, mixing social welfare reforms with pro-business economic policies. A popular leader first time around, a constitutional cap on terms in office prevented him running for a second consecutive period in office. He was followed by Jose Mujica, a former guerrilla fighter and ally in the leftist Broad Front coalition. Vazquez opposed Mujica's legalization of abortion but backed other social reforms. His endorsement of a law legalizing the production, distribution and use of marijuana has dented his re-election hopes. Vazquez says a third left-wing administration would improve conditions for the most vulnerable, including a program to sponsor full-time carers of the sick. He pledges to maintain Mujica's tight monetary policy but has not detailed how he would rein in inflation, which stands at 9 percent. Vazquez pledges to cut the above-target fiscal deficit, which stands at 3.3 percent of gross domestic product, by cutting wasteful government spending. He has ruled out new taxes or a sharp fiscal adjustment. LUIS LACALLE POU, NATIONAL PARTY Lacalle Pou is a 41-year-old lawyer touted as the fresh face of Uruguayan politics who has strived to rid the center-right National Party of its stuffy image. Lacalle Pou has tapped into a vein of discontent toward the far-reaching social reforms. He says he would try to reverse much of Uruguay's pioneering marijuana law. He also said he would not grant asylum to the six Guantanamo Bay detainees. Many Uruguayans oppose the offer Mujica made to U.S. President Barack Obama without consulting lawmakers. Lacalle Pou says taming inflation would be a priority and that he would curb fiscal spending. He would encourage the creation of more savings instruments in pesos to continue de-dollarizing the economy. Lacalle Pou has said he would reduce the fiscal deficit by 1.5 percentage points, partly through greater efficiency at state-run firms. He has also campaigned on a platform to offer tax relief, including the abolishment of a tax on pensions. His National Party favors a stronger role for the private sector. (Writing by Sarah Marsh; Editing by Catherine Evans)