It has become common to bemoan the sorry state of politics, what with all the big money, dirty tricks, image molding, partisan gridlock and general cynicism. Yet voters seem never to cease longing for a leader who can restore pride to high office and rekindle the national spirit.

Sometimes it actually happens. John F. Kennedy will be remembered for his youth and his inspiring call for sacrifice in his Inaugural Address. For all the tribulations of his presidency, Barack Obama’s election was a shining moment for Americans. Now Canada is having its moment with Justin Trudeau, the new prime minister.

Since his election victory, in which his Liberal Party soared to 184 seats from 34 in the Canadian Parliament, the 43-year-old Mr. Trudeau has exuded youthful exuberance. He rode a bus to his swearing-in, he walked through the streets carrying his kids, he mixed with the crowds. He introduced a stunningly diverse cabinet, half of it women and including two indigenous Canadians; three Sikhs, one a military hero; the first Canadian in space; and two ministers with disabilities.

His intent, he explained simply, was to “present to Canada a cabinet that looks like Canada.” When asked why an equal number of men and women, his response was even more refreshing: “Because it’s 2015.”