Born in Kawakawa on 2 March 1967, and raised in the Bay of Islands, Davis affiliates to the Ngāpuhiiwi. He received his secondary education at the Bay of Islands College from 1980 to 1984. He obtained a Diploma of Teaching from Auckland College of Education and taught at Koru School in Mangere, Bay of Islands Intermediate School in Kawakawa, before becoming principal of Karetu School. He then held employment with the Education Advisory Service and the education improvement and development project Te Putahitanga Matauranga. He was then principal of Kaitaia Intermediate School from 2001 to 2007.
Member of Parliament
In the 2008 general election Davis stood for Labour in the Te Tai Tokerau seat. He was defeated by the incumbent Hone Harawira of the Mana Party, but was still elected into the 49th New Zealand Parliament by way of the party list. He was the Labour Party's candidate in the 2011 Te Tai Tokerau by-election and was again defeated by Harawira. He unsuccessfully contested the seat at the general election later in the year. After placing second to Harawira three times and losing his seat in the 2011 election, Davis announced his retirement from politics, which ended up being temporary. Davis was selected as Labour's candidate for Te Tai Tokerau in the. As a result of Labour's Shane Jones' resignation from Parliament at the end of May 2014, Davis was eligible to assume Jones' place as he had been the highest ranking non-MP in Labour's 2011 party list. He entered the House of Representatives on 23 May 2014. The Mana Movement formed a coalition with the Internet Party prior to the 2014 general election. The coalition was registered with the Electoral Commission as the Internet Party and Mana Movement in July 2014, allowing it to contest the party vote. This strategic coalition resulted in Davis getting endorsements from Winston Peters of New Zealand First and the Prime Minister, John Key of the National Party. Even the electorate's candidate for the Māori Party, Te Hira Paenga, reminded voters of the importance of strategic voting. In this election, Davis ousted Harawira, which ended the representation of the Mana Party in Parliament. Following his election, Davis became Labour's corrections spokesperson. In 2015, Davis criticised private prison provider Serco's management of inmates, alleging 'corruption' at the Mount Eden remand facility. Following an inquiry, Serco lost its contract to run the facility and Minister of Corrections Sam Lotu-Iiga was relieved of his post. Davis also criticized the Australian government for its incarceration of New Zealand expatriates facing deportation. Davis has also drawn attention to the disproportionately high number of Māori in the New Zealand prison system; with Māori comprising 50.9% of the prison population despite making up just 15% of New Zealand's population.
Deputy Leader
On 1 August 2017, Davis was appointed as the new Deputy Leader of the Labour Party, serving under Jacinda Ardern. On 1 September 2017, Ardern corrected Davis after he publicly stated that Labour would campaign on a capital gains tax policy during the 2020 general election rather than implementing it mid-term. On 19 September, Davis indicated that he was willing to sacrifice his position as Deputy Prime Minister in order for Labour to form a coalition government with either New Zealand First or the Green Party. During the 2017 election on 23 September, Davis was re-elected in Te Tai Tokerau and defeated Mana Movement leader Hone Harawira by 4,807 votes. Following the 2017 election, Davis was appointed Minister for Māori Crown Relations, Minister of Corrections, Minister of Tourism, and Associate Minister of Education in the Sixth Labour Government. As Minister of Corrections, Davis has stressed the need to address the high rates of incarceration of Māori people. In August 2018, he called for a change to "a level of imprisonment that is simply devastating our Māori whānau and communities".