Kenyon was endorsed unopposed as the party's candidate for the electorate of Newland at the 2006 state election, where veteran Liberal MP Dorothy Kotz was retiring.

He singled out increasing the use of public transport and addressing youth employment as priorities, and there was some media speculation that his status as a young, relatively conservative father of three would be well-supported in the area of Adelaide known as the "Bible Belt".

At the 2014 state election, Kenyon's seat became Labor's most marginal on a 51.4 percent two-party vote from a 1.2-point swing.

[3][4] Since his election, Kenyon successfully advocated within the Labor party for the expansion of uranium mining with Paul Holloway, including the abandonment of the Three-Mine Policy.

In an Opinion Editorial for The Australian he wrote: "It's time we in the ALP gave up pretending that nuclear energy is Satan's power supply of choice...

While the Commission was undertaking its work, Kenyon became a public advocate for the importation of spent nuclear fuel to South Australia for storage and disposal.