The National Super Alliance (NASA) was formed in 2017. It aims to increase opposition chances of defeating President Uhuru Kenyatta. The announcement will be made just over 100 days before voting, but the country's ruling Jubilee party has said NASA's delayed candidacy selection only highlights its disorganization amid an election campaign plagued by violence.

On Thursday, President Kenyatta said he would not tolerate any violence in the lead up to Kenya's national election. The president's warning comes after chaotic party primaries resulted in bloody scuffles between rival political supporters. 

"I and my administration are concerned that those incidents of chaos and violence that have sometimes featured in such primaries may be repeated," Kenyatta said in a televised press briefing at State House in the country's capital Nairobi. "Let me say clearly, again,a culture of hooliganism during the electoral process must not and will not be allowed to gain currency and acceptance."

This year's election comes a decade after disputed poll results fueled fighting that left more than 1,100 dead and hundreds of thousands displaced.

Election-fueled violence

The Kenya National Commission on Human Rights (KNCHR) as well as the National Democratic Institute (NDI) have warned of possible violence during this year's elections.

Primaries to choose candidates for local government and parliament have already been affected by violence and dramatic last-minute floor-crossings. Dozens were injured earlier this month at the Nairobi headquarters of opposition party Orange Democratic Movement (ODM), when supporters of one senate nominee drew guns claiming her rival had already secured the party ballot.

Local media also reported on Wednesday that fistfights between rival supporters left at least nine injured.

Ethnic and political alliances

Politics in the East African nation is decided largely along ethnic lines, with political alliances typically based on who can lure which votes from Kenya's influential five main ethnic groups.

Kenyatta, 55, is seeking a second and final term in office, running alongside his deputy William Ruto. The two men allied in 2013, bringing together two ethnic groups, Kenyatta's majority Kikuyu and Ruto's Kalenjin, who had violently clashed in 2007.

The wealthy son of the country's first president, Kenyatta managed to win the vote four years ago despite being charged with crimes against humanity by the International Criminal Court (ICC). The charges, over his role in the 2007 violence, were later dropped.

In an attempt to oust the powerful party, five opposition heavyweights united under NASA. They have spent months agonizing over the winning combination of flag-bearers that will draw in the most votes from key ethnic groups.

NASA also ushered in new member Isaac Ruto on Thursday. The Governor of the southwest Bomet region brings with him support from Kenya's Rift Valley, the largest province in the country.

"We want to say no to misrule, we cannot continue like that, we must eliminate tribalism in Kenya, there are so many issues I have raised with the current regime for more than four years but they have continued to rubbish it and abuse everybody from Turkana all the way to Loitokitok. Is that the country we want?" Ruto said during his induction. "I cannot continue to associate myself or my supporters with such a ridiculous regime."

A confident opposition

Despite the upcoming late candidacy announcement, NASA members said Thursday's addition of Ruto highlights the diversity of its campaign. The support Ruto brings with him will help the opposition party remove Kenyatta from power, they said.

"The unity of our nation is within sight, I am proud to welcome honorable Isaac Ruto to the NASA summit, with his entry we launch a new march towards August 8 general elections," principle party member and former Prime Minister Raila Odinga said. "We will liberate Kenyans from the yoke of Jubilee."

Odinga, a veteran opposition leader, is a frontrunner for the opposition presidential candidacy. If chosen, the 72-year-old will face his last shot at the presidency after losing three past elections. He blamed his 2007 and 2013 losses on vote rigging.

This year, some 19 million voters are registered to take part in the election, pending a final audit to remove dead voters or double listings.

Andrew Wasike contributed to this article.