Justin Trudeau, Canada's recently elected prime minister, is visiting the US this week. Thursday evening he'll be dining at the White House — the first official state dinner for a Canadian leader in roughly 20 years.

People are excited. And I mean really excited.

"Seriously, with his looks, heart, and mind, he’s dreamy," an anonymous senior Obama administration official told Politico. The official went on to refer to Canada's leader as "my new political crush."

This hilariously off-message Obama official is far from alone: Trudeau-mania is definitely a thing. Since Trudeau swept to power in October elections, his good looks, charm, and earnestly left-wing politics have made him into an international celebrity. Think Obama in mid-2008, before all the partisanship and bitterness.

And, like Obama, the celebrity is backed up by a pretty substantive policy agenda. Trudeau's election has ushered in major new policy shifts on issues ranging from Syrian refugees to marijuana legalization.

So here's a brief guide to Canada's new dreamboat prime minister: where he comes from, why he's become such a phenom, and what his agenda actually is.

Trudeau is a scion of a major Canadian political dynasty

Though Trudeau's persona resembles Obama's, his background is closer to George W. Bush — except imagine if W had been Ronald Reagan's son rather than George H.W.'s.

Trudeau's father, Pierre, was prime minister for a huge stretch of time: from 1968 to 1979, and then again from 1980 to 1984. He remains the towering figure in the history of Canada's Liberal Party and Canadian liberalism, rivaled only by his predecessor, Lester Pearson.

"Progressive modern Canada was created largely under the rule of [Pearson and Trudeau]," Guy Lawson writes in the New York Times. He continues:

The earliest major political initiative of Pierre Trudeau in the late ’60s was to decriminalize homosexuality. ‘‘The state has no business in the bedrooms of the nation,’’ he said. In rapid succession, Trudeau legalized abortion, funded the arts and promoted a race-blind immigration policy.

Trudeau wasn't just accomplished; he was also a media sensation. In 1981, after he had separated from his wife, the actress Kim Cattrall (you know her as Samantha in Sex and the City) called up Pierre to ask him out.

So, if anything, even the Reagan/Bush comparisons understates Justin Trudeau's family legacy: His father was both a towering historical figure and a cultural icon. Almost a cross between FDR and JFK.

Trudeau's political résumé is extraordinarily thin

Early in life, Trudeau didn't seem particularly interested in the family business. After attending McGill, Canada's most prestigious university, he worked as a snowboarding instructor, a bouncer at a bar in British Columbia, and a high school math teacher.

He started getting national political attention in 2000 after giving a moving eulogy at his father's funeral. He won a parliament seat on the Liberal ticket in 2008, and ultimately became the party's leader in 2013.

During this time, a lot of Canadian political observers dismissed him as a lightweight — a somewhat ironic label, given the fact that Trudeau had beaten a Conservative legislator in a televised boxing match in 2012. Yes, seriously:

Justin Trudeau weighing in at a charity boxing match 3 years ago @reuters pic.twitter.com/6yUgBEUOoA — tom (@tomwoodau) October 21, 2015

What was I saying? Ah, yes, lightweight. The knock was that Justin traded on Pierre's legacy but had no real experience or command of the issues.

The incumbent Conservative Party, for example, ran an ad in the 2015 election where a fake "hiring committee" looked at Trudeau's résumé for prime minister. They decide that despite his "nice hair," Trudeau was too inexperienced to be trusted with power. The ad ends with what became a major anti-Trudeau slogan: "He's just not ready."

It wasn't clear whether Trudeau would ever surmount this perception. For most of their campaign — right up until the end, in fact — Trudeau's Liberals trailed either the Conservatives or the left-wing third party, the New Democratic Party (NDP).

So when the Liberals actually won the October 19 vote outright, largely on the back of anti-Conservative sentiment, a lot of people weren't really sure what they'd be getting from a Trudeau-led government. What came next seems have surprised almost everyone.

How Trudeau became not just prime minister but a celebrity

There are basically two parts to Trudeau's rise to international celebrity: the toxic legacy of his predecessor, Stephen Harper, and the fact that he's just too damn charming for words.

For the Canadian left, Conservative Prime Minister Stephen Harper's defeat in 2015 was an extraordinary relief. Harper first took power in 2006 and had governed in a nasty, fairly divisive fashion. He cast himself as the champion of "old stock" (read: white) Canadians. He exploited wedge issues, like prejudice against Muslim immigrants, to hold on to power in an overwhelmingly liberal country. His Conservatives managed to govern for more than a decade by taking advantage of splits between Canada's left-of-center parties, winning a series of elections without ever securing the loyalty of the median Canadian voter.

The prospect of more than a decade of Harper in power was, for many Canadian liberals, unbearably terrifying. In American terms, it would have been like George W. Bush running for a third term in 2008 — and having a serious shot at a victory.

So when Trudeau won in 2015, Canadian liberals were overjoyed. Even some leftists who voted for the NDP, and not the Liberals, were thrilled just to see Harper out.

Consequently Trudeau took power with a deep reservoir of goodwill. And then he proceeded to build on that by being absolutely adorable.

I don't just mean handsome (though let's be real: I do kinda mean handsome). It's that Trudeau displayed an impressive deftness at picking up on left-wing social issues, the kinds of things his father also emphasized, and highlighting them in a way that made him seem compassionate, thoughtful, and open-minded.

Trudeau's vision of Canada is one that appeals to many Canadians' sense of what their country, at its best, should be: an open, tolerant, progressive beacon for the rest of the world. As one young Canadian put it in an interview with Bloomberg, Harper "pushed Canada to act just like the United States. At least with Trudeau, we have our identity back."

While the Harper government messed with Canada's asylum process to block Syrians from entering, Trudeau announced a plan to admit a total of 25,000 new Syrians by March. In December, he personally greeted the first batch of refugees on their arrival in Canada:

He committed to attending Toronto's Pride Parade, the first such prime minister to do so:

He announced a commitment to do appoint a Cabinet that "looked like Canada," and then went on to appoint the most diverse Cabinet in the nation's history:

He talks about feminism in compelling, meme-worthy bites:

Trudeau is the perfect prime minister for the social media age. He intuitively gets the kind of affirming identity politics that speaks to huge numbers of people on the internet.

And if you go viral, it's often not just in one country. Trudeau's inherent charming appeal — his decency, tolerance, and cuteness — made him into a global icon for cosmopolitan liberalism, especially in contrast to the increasingly foul politics you're seeing in other parts of the world.

In a contest between Donald Trump and Justin Trudeau for the world's heart, Trudeau wins in a knockout.

Justin Trudeau has an ambitious policy agenda

It's really easy, when you're talking about Trudeau, to get distracted by the cuddliness of his politics and ignore the actual, er, politics. But it turns out that if you actually pay attention to Trudeau's agenda, he's taking Canada in a profoundly new and more liberal direction.

One personal priority of Trudeau's, for instance, is nationwide marijuana legalization. He campaigned on it, and promised to get working on it "right away" after being elected. It's a bit tricky to implement: His government has to get around international anti-drug treaties as well as some resistance from Canada's provinces.

On economics, Trudeau's government has already lowered taxes on the middle class while increasing them on the rich (people making $150,785 or more). Most radically, his government is considering creating a basic income — a system wherein the government unconditionally pays every Canadian a certain amount of money per year.

His refugee policy has gone well beyond letting more Syrians into Canada. He's already given an additional $75 million to the UN High Commission on Refugees, and fully restored a federal program (weakened by Harper) that would provide temporary health benefits to refugees in Canada.

Trudeau has also restructured Canada's role in the fight on ISIS. He ended Canada's participation in bombing runs against the group, which was quite minimal to begin with. But he stepped up Canada's support role, tripling the number of Canadian trainers on the ground and committing Canadian special forces to help target airstrikes hitting ISIS targets.

This recommitment was celebrated by the United States.

"The Canadian announcement is the kind of response the secretary’s been looking for from coalition members," Pentagon spokesperson Peter Cook said at a press briefing, "as the United States and coalition partners push to accelerate the campaign against [ISIS]."

The warm response to Trudeau's ISIS announcement is emblematic of the current state of US-Canada relations. Under Trudeau, Canada and the US are on better terms than they have been in years.

Under Harper, US-Canadian relations were polite but not especially close. The ideological gap between Obama and Harper was just too large to breach.

Trudeau, by contrast, shares Obama's generally progressive commitments. Shortly after his election, Trudeau reached out to Obama. They immediately struck up a warm rapport, partly based on Obama giving Trudeau advice about being young, exciting political phenom entrusted with power.

‘‘There was an air of mentorship but not in a paternalistic way,’’ Ben Rhodes, Obama’s deputy national security adviser, said to the New York Times. ‘‘Trudeau’s going to be on the stage for a long time. He’s got a ton of talent.’’

So tonight's state dinner isn't just a formality. It's a celebration of a strengthened US-Canada relationship — as well as Justin Trudeau's bold, sexy vision for a new Canada.