When Britons go to the polls on Thursday to choose the 58th Parliament, The New York Sun will be rooting for Boris Johnson. It might seem preposterous for an American publication to make an endorsement in a British election. Then again, too, one wag noted, if the Sun hadn’t, at the last minute, emerged as the only national paper to endorse Donald Trump, Secretary of State Clinton might be president.

More seriously, it’s hard to think of many political causes in which we’ve been more invested over the years than that of an independent Britain. We formed our view, in the 1980s, by covering the European Union for a great newspaper (in our case, the Wall Street Journal). It’s the same method through which Mr. Johnson reached his conclusions about the EU, by covering it for a great newspaper (in his case the Daily Telegraph).

Our enthusiasm for Mr. Johnson stems partly, if only partly, from our regard for the methodology through which he reached his conclusions. Not that his and ours today are identical in respect of Brexit. Mr. Johnson backs a Brexit deal with the EU. We favor a no-deal Brexit, a clean break, as the correct reading of the 2016 referendum and, in any event, the ideal resolution. In this sense, Nigel Farage has the better Brexit blueprint.

Yet Mr. Farage is not standing for premier — or even a seat in the Commons. And heroic as he is, our own estimation is that the cause of Brexit would not have prevailed in the 2016 referendum based on Mr. Farage’s campaign alone. That was focused on the negative features of the EU, its lack of democracy and the requirement of open borders to the bloc. In that sense, the independence campaign was oddly backward looking.

It wasn’t until Mr. Johnson entered the fray that the tide began to swell for the astounding victory of Brexit. This was owing not only to Mr. Johnson. The laurels can be shared by the intelligentsia that came together as the Bruges Group after Prime Minister Thatcher issued in 1988, at Bruges, Belgium, her warning about Europe’s socialism. We particularly admired the argument for Brexit by Thatcher’s former chancellor, now Baron Lawson.

What they, with Mr. Johnson in the van by 2016, brought to the hustings was a focus on the upside of Brexit. This is what Mr. Johnson called the “sunny uplands” of liberty. That’s what illuminated the fact that Brexit, at bottom, is not about xenophobia. The xenophobes turn out to be the Europeans. Also, sadly, the Labor Party that, under Jeremy Corbyn, has become riddled with anti-Semitism.

The Wall Street Journal’s Joseph Sternberg, formerly of the Sun, reckons Mr. Corbyn’s “lack of basic decency” has become an issue in Thursday’s vote, along with, as Mr. Sternberg lists them, the socialized National Health Service, university tuition fees, Scottish separatism, criminal-justice reform, trade with Donald Trump’s America, rail fares, broadband provision, and pension payouts to baby-boomer women.

Brexit, though, is the existential issue. We don’t take the outcome for granted, either. Mr. Johnson’s Conservative Party may be leading in the polls (the Conservatives, according to Oddschecker.com are the only odds-on bet to win a majority in the Commons). Then, again, too, so was Prime Minister May when, in the spring of 2017, she called her snap election thinking she’d expand her majority. Instead, she lost it in a catastrophic defeat.

It’s not that we predict such a fate for the Conservatives on Thursday. We just acknowledge the possibility. To us the overwhelming logic is for voters to empower Mr. Johnson and the Conservatives to move with confidence in extracting Britain from Europe, redeeming the referendum of 2016, expanding the special relationship with America, and setting the stage for a new birth of the liberty and political economy of which Britain was once a headwater.