The Kenyatta-Ruto alliance fell apart ahead of the next election in 2022. Gachagua sided with Ruto and paid the price -- he was arrested multiple times on corruption charges which he said were politically motivated attacks by Kenyatta.
In one infamous moment in July 2021, he said police raided his home and stripped him near-naked in front of his children.
But Ruto and Gachagua had the last laugh, joining forces and winning the hard-fought election, presenting themselves as anti-establishment figures against the dynasties that had long-dominated Kenyan politics.
It was a particularly surprising leap for Gachagua who had a limited national profile before the campaign.
He managed to rally many within his Kikuyu tribe in Mount Kenya, presenting a new figurehead for a region long dominated by the Kenyatta family.
'I am a truthful man'
That local popularity has lately backfired, with Gachagua accused by critics of playing too heavily on outdated tribal loyalties.
The taint of corruption has also been hard to shake.
He was charged in 2021 with acquiring unexplained wealth totalling more than 7.3 billion Kenyan shillings ($57 million).
That case was dropped when he and Ruto took office, but lawmakers accused him of amassing 5.2 billion shillings ($40 million) during his two years as deputy president, despite an official salary of $93,000.
He says his wealth comes from his family's business dealings in real estate, hospitality and construction.
"All the problems that I am going through is because I am a truthful man," he said last month, claiming he is disliked for his blunt style.