South Australian senator Lucy Gichuhi has given the Turnbull government a handy boost ahead of parliament's return by joining the Liberal Party.
The surprise move eases the coalition's pain in the Senate, reducing the size of the crossbench and boosting its numbers to 30.
The Kenyan-born crossbencher, who was catapulted into federal parliament to replace disqualified Family First senator Bob Day, hit the streets with senior South Australian Liberal Simon Birmingham on Saturday.
Senator Gichuhi said learning from Liberal politicians over the past nine months had convinced her to join the party.
"For me, this is an opportunity to learn how to serve South Australia," she told reporters in Adelaide.
"I have been a student - I mean literally, a student - learning from parliamentarians because as you may all know I'm not coming from a political background."
Senator Gichuhi said Liberal Party values closely aligned with her own core beliefs.
Senator Birmingham said his party's new recruit would help the Liberals connect with communities from a broad diversity of views and backgrounds.
"This is a wonderful testament to the fact that we have, over the last year, worked co-operatively with Lucy in the Senate and here in South Australia to build a strong relationship," he said.
"I am confident that in Canberra Lucy will be a strong advocate for South Australia and for Liberal values, and that here in South Australia, Lucy will continue to be a hard-working senator."
The government will now require the votes of nine of 11 crossbenchers to pass legislation opposed by Labor and the Greens, rather than 10 of 12.
Prime Minister Malcolm Turnbull is ecstatic about the surprise manoeuvre, which comes days before parliament's first sitting day for the year on Monday.
"She is a true Australian success story and we are honoured that she has chosen to join the Liberal Party," Mr Turnbull said.
"Lucy's values are fundamentally Liberal values; freedom of choice, conscience, thought and belief, a fair go, mutual obligation and contributing to society."
Senator Gichuhi took Bob Day's seat following a vote recount after he was ruled ineligible to stand for election.
She then quit Family First after it merged with the Australian Conservatives.
Her defection is another boost for Mr Turnbull after the resignation of Labor MP David Feeney who was unable to prove he was no longer a British citizen.
The Greens are a big chance to win the by-election in Mr Feeney's Melbourne seat of Batman, which would give the government some breathing space in the lower house where it currently holds a one-seat majority.
