The former Revolutionary Armed Forces of Colombia, or FARC, are now a political party fielding candidates under a 2016 peace accord that ended Latin America's longest and most potent insurgency.

A smaller rebel group, the National Liberation Army, is observing a truce on Sunday. The government of President Juan Manuel Santos, whose term ends on August 7, is trying to reach a similar peace accord with those guerrillas -- but talks have been suspended because attacks have resumed.

Abstention is usually around 60 percent in Colombia, but the elections will still be crucial for the future of the peace process and the survival of the left.

And they could also set the stage for the return of right-wing politicians who could allude to the economic crisis in neighboring socialist-ruled Venezuela as a scare tactic. Members of the right have also called to amend the peace accord reached with the Common Alternative Revolutionary Force, as the FARC now calls itself, using the same Spanish acronym.

- Rough start -

The former rebels come into the election as a leftist force that still must confess to wartime atrocities and pay reparations to victims.

The peace accord, which established a special system of justice for wartime abuses and is due to take effect this year, guarantees the FARC at least 10 of the 280 seats in congress.

But the FARC still have to take part in the election, and none of the public opinion polls carried out shows it capable of winning more than those 10 seats.

"Even though they will probably not achieve the result they hope for, what is at stake for the FARC is positioning and the possibility of establishing itself with an eye to what really interests it politically: elections" for mayor and governor in 2020, said Carlos Arias Orjuela, a political consultant at Externado University.

What is more, the FARC suffered a setback Thursday with word that its leader Rodrigo "Timochenko" Londono will not run in the presidential election in May as previously planned because he suffered a heart attack.

- Eyes on the presidential vote -

Sunday's legislative elections kick off an election season that will see a successor to Santos chosen on May 27.

Leftist and conservative coalitions will pick their candidates in internal party proceedings.

An ex-guerrilla and former mayor, Gustavo Petro, is heavily favored to be the leftist candidate while Ivan Duque is the favorite for the right, and has the support of senator and former president Alvaro Uribe.

Both men are doing well in pre-election polls.

But the conservative Uribe could end up being the big winner: he could not only hold on to his seat Sunday but also end up leading the conservatives in the legislature.

- Return of hardwing conservatives -

After eight years with a government and legislature that produced the peace accord with the communist guerrillas, on Sunday hardline conservatives who oppose the agreement could win an absolute majority in congress.

The outgoing Santos led the Social Party of National Unity, a center-right grouping that was the country's largest. But it fell into disrepute because of corruption scandals, and is not even fielding a presidential candidate in May.

Its decline is likely to benefit more right-leaning conservatives in the legislative vote.

The Colombian left comes into the vote fragmented and shunning any notion of alliance with the FARC. Its goal is basically to win enough votes to keep its head above water as a minority party in congress.

- Corruption and ill repute -

Colombia is deeply divided by the peace accord with the FARC, and Congress today is the worst viewed institution in the country, with a disapproval rating of 84 percent in a Gallup poll carried out in December.

Authorities are investigating dozens of lawmakers for suspected corruption, and 11 have lost their seats or are in jail.

The most high profile cases involve alleged shady dealings with the Brazilian construction giant Odebrecht, which waged a vast campaign of bribery in 12 countries as a way to win juicy contracts.

Prosecutors here estimate the company paid out $27.7 million in bribes in Colombia.

And 80 of the 2,730 candidates in Sunday's voting are suspected of embezzling government money or of having links to politicians convicted of being tied to far-rightwing paramilitary groups, activists say.