Geoff Brock

Brock increased his primary vote to 45.2 percent and two-candidate vote to 58.8 percent at the 2014 election. The election resulted in a hung parliament with 23 Labor seats, 22 Liberal seats, and two independents. The balance of power was held by crossbench independents Brock and Bob Such. Such did not indicate who he would support in a minority government before he was diagnosed and hospitalised with a brain tumour and took medical leave one week after the election. University of Adelaide Professor and Political Commentator Clem McIntyre said Such's situation virtually guaranteed Brock would side with Labor. With 24 seats required to govern, Brock backed Labor. McIntyre said:

Martin Hamilton-Smith resigned from the Liberals and joined the Labor cabinet two months after the election. Labor achieved majority government when Nat Cook won the 2014 Fisher by-election which was triggered by the death of Such. Despite this, the Jay Weatherill Labor government kept Brock and Hamilton-Smith in cabinet, giving the government a 26 to 21 parliamentary majority.

In the Weatherill Ministry, between 2014 and 2018 Brock has served as the minister with responsibilities for regional development and for local government.

Brock increased his primary vote to 37.7 percent and two-candidate vote to 57.5 percent at the 2010 election. Labor won from the Liberals the two-party-preferred vote on 50.1 percent.

Brock had a shock win at the 2009 Frome state by-election, defeating the Liberal candidate Terry Boylan. He had a high local profile prior to the election, having served for almost six years as council mayor. Independent Senator Nick Xenophon also campaigned for Brock.

On 23.6 percent of the primary vote and 51.7 percent of the two-candidate-preferred vote, Brock's election depended on preferences from Labor, Nationals SA, and the SA Greens, the former two having placed him second on their how-to-vote card. His own how-to-vote card saw him preference the Nationals, Labor, Liberal, Greens, and One Nation, in that order. The by-election was closely contested, with the result being uncertain for over a week. Initial reports suggested a slight swing to the Liberal candidate Terry Boylan on the two-party-preferred count against Labor, with Brock close behind Labor. By 21 January 2009, both the ABC's Antony Green and the state electoral office were indicating a 2-point swing against the Liberals toward Labor on 51.4 percent, but not enough to lose the seat. Liberal leader Martin Hamilton-Smith claimed victory on behalf of the party.

Brock had worked in Port Pirie's lead smelter, which was eventually acquired by Nyrstar, since arriving in the town in 1976. He was first elected to the Port Pirie Regional Council (at that time a City Council) in 1989, and served on numerous community committees before being elected mayor in May 2003, defeating sitting mayor Ken Madigan by 3,297 votes to 2,173. He retired from Nyrstar in September 2007, and he and his second wife Lyn have 12 grandchildren between them.

Geoffrey Graeme Brock (born 1950) is a South Australian politician, representing the seat of Frome in the South Australian House of Assembly as an independent since the 2009 Frome by-election. Following the 2014 election Brock was Minister for Regional Development and Minister for Local Government in the Weatherill Labor cabinet until it was defeated at the 2018 election .