The phrase "by a very small margin" is correct and can be used in written English.
For example: "The other candidate won the election by a very small margin."
Justice Prosser won the April election by a very small margin, prompting a recount.
Joanna Ciechanowska, director of POSK's gallery says: "I hoped by a very small margin we'd stay in.
Then I ran again in 1974 and won my seat back by a very small margin, and then ran in '76 and won by an even smaller margin.
Had he won the votes on election night in Florida, even by a very small margin, and had George W. Bush conceded, I would accept him as my president.
But at the end of nine hours rehearsal of stale arguments made in bad faith the general synod took a decisive turn into fantasy, or stumbled over its own rules, and failed, by a very small margin, to gain the complicated majorities required to make women bishops.
Even those who may be legitimately worried about Russia's meddling know it's not hard to draw the line from A to B to C: The Russians meddled on Trump's behalf, and Trump won by a very small margin (about 80,000 votes), so it's quite possible Russia tipped the scales in the election.
Despite the clamor in his stronghold of Valencia, recent polls show Mr. Aznar's center-right Popular Party ahead of the Socialists by just four percentage points, a very small margin in a country that is notoriously difficult to survey.
By going for the lines and shooting for the corners, he has a very small margin of error in his game.
