MacLauchlan, 60, ran unopposed for the party's leadership after Robert Ghiz announced he was stepping down after eight years as premier.
He becomes the province's 32nd premier on Monday when Ghiz formally resigns.
One of the first big decisions MacLauchlan will have to make — in addition to naming a cabinet — revolves around election timing.
P.E.I.'s next election can take place as late as April 2016, but there is speculation MacLauchlan could move that forward to this spring rather than run in a byelection to get a seat in the legislature.
The new Liberal leader has been coy about his election plans, although Robert Vessey is stepping down as minister of transportation and infrastructure renewal to become his chief of staff. That also opens MacLauchlan's home riding of York-Oyster Bed for him to run in.
MacLauchlan told reporters he could have more to say about his election plans on Friday.
"I'd invite people to come to a dinner on Feb. 27 in the York-Oyster Bed district and there may be some news there," he said.
Whenever an election is called, the Opposition Progressive Conservatives will have a new leader as well at the party's helm. The party held advance polls Saturday in its three-candidate race to be decided next weekend at another leadership convention in Charlottetown.
MacLauchlan, a lawyer, was president of the University of Prince Edward Island from 1999 to 2011. Before that he was dean of law at the University of New Brunswick. He also taught at Dalhousie University in Halifax and studied at Yale University in the United States.
Born in the rural community of Stanhope, MacLauchlan is openly gay and acknowledged the support of his partner Duncan McIntosh, artistic director of the Watermark Theatre in Rustico, in his acceptance speech.
MacLauchlan outlined his broad goals as premier in the speech, which include improving the economy, open government, citizen engagement and dealing with demographic change as the province's population ages.
Boosting trade and immigration were highlighted by MacLauchlan as ways of pushing economic growth.
"Prosperity starts with growing our economy," he said.
"We can and must do better. We have the goods and the services, and the culture and the work ethic to back it up."
As his acceptance speech came to an end, MacLauchlan used the lyrics "You gotta tune your attitude in" from a song by the late Stompin' Tom Connnors, who he referred to as the province's pre-eminent philosopher.
"I have my attitude tuned in," he said.
Prof. Donald Savoie, who has known MacLauchlan for about 20 years, said recently he expects Canada's newest premier to make an impact among his national peers.
"Let it be a warning to other premiers and the prime minister, this guy is going to be articulate, he's going to be forceful and brings to the table a work experience and life experience that is rarely seen in politics," said Savoie, who holds a Canada research chair in public administration and governance at the University of Moncton.
MacLauchlan will get a chance to test his political leadership skills right away. When he replaces Ghiz on Monday he also becomes chairman of the Council of the Federation, which is made up of the country's premiers.
The Liberals hold 23 of the legislature's 27 seats.
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