SA Best, the party that promised to be a third force in South Australian politics, has officially closed its chapter in state political history after its final remaining member of parliament lost their seat in the March election.Formed by Nick Xenophon in 2017 ahead of the 2018 state election, the party hand-picked 36 candidates and was tipped by some pollsters as a party which could hold the balance of power.Connie Bonaros was one of two candidates elected to the upper house after 14 years as an advisor for Nick Xenophon. Sitting in the SA Best campaign room surrounded by election materials, which included a life-size cardboard cutout of Mr Xenophon, she reflected on her time in office "Naturally, I'm sad that it's come to an end," Ms Bonaros said. "We're a minor party, and we know minor parties come and go, and they leave behind them — if they're lucky — legacies.Eight years ago, in the lead-up to the 2018 South Australian election, Ms Bonaros was one of dozens of candidates running for election under the SA Best banner, as the ambitious centrist party emerged as a frontrunner in the polls.Nick Xenophon had quit federal parliament to create the state party and, according to polling by Newspoll and Galaxy, close to half of South Australians wanted him elected as the next premier.The poll results sparked a fierce campaign against SA Best from both of the major parties, but by election day the predictions fell short