Raj Sherman, an emergency room doctor, had been sitting as an Independent in the legislature but announced he was unanimously invited by the eight other Liberal legislature members to join caucus.
The 45-year-old Edmonton MLA says his priorities are to reinvigorate the party at the grassroots level and get candidates nominated for an election that could come as early as this fall.
He works two shifts a month in an Edmonton emergency room, but says he'll likely have to set that aside to focus on party matters.
He says there's lots of work to be done — the party has just nine members in the 83-seat legislature, has nominated just 10 candidates, and has seen many of its constituency associations in the major cities lapse into inactivity.
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Sherman won a weekend vote by party supporters to replace David Swann as leader.