Brazil's presidential candidates at a glance

Brazil's presidential election, which opens with the first round on October 7, is seen as the most unpredictable in decades.

Brazil's presidential election, which opens with the first round on October 7, is seen as the most unpredictable in decades.

With former president Luiz Inacio Lula da Silva ruled out over a corruption conviction and the widely unpopular incumbent Michel Temer avoiding the embarrassment of what would surely be a humiliating bid for re-election, a new breed of lesser-known politicians are taking their chances.

Here's what you need to know about the biggest names in the race:

Bolsonaro: Tough-talking ex-military man

Former army captain Jair Bolsonaro, 63, is often called Brazil's Donald Trump.

He not only gets away with saying the outrageous but uses the attention to bolster his claim of being an outsider combatting the corrupt, incompetent elite.

Among his regular targets are gays, women and torture victims under the 1964-85 military dictatorship.

Despite the fresh image, boosted by enthusiastic use of social media, Bolsonaro is actually a long-serving member of Congress.

The right-winger is not being probed for corruption -- a real plus in a political system where every party and much of the government are riddled with graft scandals.

Since Lula was ruled out of the running due to Brazil's "clean slate" laws, Bolsonaro has led in the polls, carried by his market-friendly and tough-on-crime policies.

The injuries he suffered in a knife-attack a month ago also turned him into a victim, further boosting his popularity. He was released from hospital on Saturday.

He is with the Social Liberal Party, which despite its name is conservative.

Haddad: Lula's replacement

It's been barely three weeks since Fernando Haddad, 55, was picked to replace Lula as the leftist Workers' Party (PT) candidate, although it had been in the pipeline for months.

His first difficulty was to build a profile once the all-enveloping shadow of Lula was lifted. Despite previously having held the post of mayor of Sao Paulo, he was a virtual unknown outside Brazil's biggest city.

The son of a Lebanese immigrant, he's a political science professor at Sao Paulo University and during Lula's government worked as Minister for Education.

He's surged into second place in the polls since Lula was dropped from the ballot, boosted by a transfer of PT loyalists switching their allegiance to him.

But like the jailed icon Lula and his hand-picked successor as president, Dilma Rousseff, Haddad has faced corruption accusations linked to his campaign during municipal elections in 2012.

And if there's one thing Brazilians are fed up with, it's corruption.

Gomes: Fiery leftist

Some saw Ciro Gomes, who has also made two failed presidential attempts in the past, as someone capable of capturing the country's huge leftist vote in the place of the imprisoned Lula.

Gomes, 60, is running with the Democratic Labor Party but has failed to garner coalition support from other leftist parties, leaving him isolated.

He is seen as a volatile personality with a history of lashing out in colorful language at everyone from Lula and Temer to the country's police.

He has also failed to attract many of Lula's supporters, leaving him a distant third behind Haddad and set to miss out on the top job once again.

Alckmin: 'Not a showman'

In a country exhausted by scandal and economic disarray, former Sao Paulo governor Geraldo Alckmin, 65, bills himself as the adult in the room. "I am not a showman," he says proudly.

From the big centrist Brazilian Social Democratic Party, or PSDB, Alckmin is hardly the outsider that pollsters believe Brazilians are looking for in this election.

He was expected to gather strength after securing in July the backing of the multiple-party, center-right alliance that dominates Congress.

That made him the key establishment candidate and, among other advantages, entitled him to an especially large slice of TV and radio advertising time.

But that didn't translate into voter intentions and he is stuck on single-digit poll numbers.

His first attempt at the presidency in 2006 saw him beaten in the second round by the infinitely more charismatic Lula.

Marina Silva: The survivor

She's black, once worked as a maid and has never been charged with corruption: meet Marina Silva, one of Brazil's least typical politicians.

Silva, 60, overcame a harsh childhood in the Amazon to become a courageous environmental campaigner, before bursting into the heavily male-dominated world of national politics and serving as environment minister under Lula.

The center-leftist made two strong bids for the presidency in 2010 and 2014, so she is hardly unknown. However, she is frequently criticized for appearing to go quiet between the campaigns and bending her message to the point where many Brazilians no longer know quite what she stands for.

Running with her own REDE party, she had been battling Bolsonaro for second place behind Lula in earlier polls but since her former boss was removed, Silva's popularity has plummeted alarmingly and she now appears a no-hoper.