Flávio Bolsonaro is in pole position to win Brazil’s presidential election, after a far-right tsunami propelled him to a shock first-round victory over the incumbent, Luiz Inácio Lula da Silva, leaving progressive voters reeling.

The 45-year-old rightwing candidate received 56.1m votes to Lula’s 53.8m – 47.03% to 45.16% – meaning the 80-year-old leftwinger has a mountain to climb if he is to bounce back in the second round on 25 October. Never, since the return of democracy to Brazil in 1985, has the first-round runner-up managed to turn the game around and win the second ballot.

“Miracles are possible in politics. But I don’t see that happening,” the political scientist Miguel Lago said of Lula’s chances of snapping back. “I don’t see Flávio losing this election now.”

Speaking outside the White House on Monday, Donald Trump told reporters: “Well, it’s a big victory: close but a very, very big victory. Amazing, actually.”

Trump, who is a longtime ally of the Bolsonaro family, predicted the runoff would be “a very close election”