Former Tanzanian Prime Minister Edward Lowassa was the surprise guest at a cultural ceremony in which Maasai elders said they were backing Kenyan President Uhuru Kenyatta for re-election on August 8.
The more than 100 elders drawn from Tanzania and Kenya also included several Tanzania MPs, exposing rivalries at the top of the two countries' politics with the friendship between President John Magufuli and Raila Odinga, President Kenyatta's main challenger, not a secret.
President Magufuli, however, has not publicly endorsed Mr Odinga as diplomatic etiquette and AU protocols require that a sitting head of state should not be seen to interfere in another country's internal affairs.
He has been forced, however, to deny that he was supporting Mr Odinga and had allowed him to set up a tallying centre in Tanzania.
This was amid speculation that their rapport was the reason for an incessant diplomatic war between Kenya and Tanzania that caused the breaking of ranks on regional projects like the pipeline, the standard gauge railway and the trade partnership with Europe.
During the meeting at the Maasai cultural shrine of Suswa in Narok County, Mr Lowassa asked the community and all Kenyans to re-elect President Kenyatta. This was the second time he had done so, the first having been during the burial of former Kenya Interior Minister Joseph Nkaissery last month.
Mr Lowassa said he supported President Kenyatta for being democratic, bringing unity to a country that was polarised along ethnic lines when he took office and for supporting the East Africa Community.
"I support Uhuru Kenyatta because he is a charismatic and democratic leader whom l know will enhance East African integration once in power," said Mr Lowassa.
President Kenyatta announced at the meeting plans to make secondary education in boarding schools in pastoralist areas free.
Mr Lowassa is a traditional Maasai leader known as Laigwanan, who usually commands respect among the ethnic group.
Chadema spokesman Tumaini Makene said Mr Lowassa was echoing the party's declaration in June that it would support President Kenyatta because he had demonstrated leadership in working with the opposition unlike Mr Odinga who "supports oppression in Tanzania."
However, analysts do not see Mr Lowassa's stance having any impact on the Kenya election outcome.
"He is little known in Kenyan politics," said Prof Benson Bana of University Dar es Salaam.
He said Mr Lowassa's position was personal just like President Magufuli had supported Mr Odinga during the previous election in Kenya in 2013.
"This will in no way affect diplomatic relations between Kenya and Tanzania because the two countries' relationship are guided by bilateral agreements which have nothing to do with personal friendship between Mr Kenyatta and Mr Lowassa," Dr Bana said.