New Delhi, Oct. 27 -- Brazilian President Luiz Inacio Lula da Silva staged a comeback after a first-round setback to win a fourth term in office, securing 51.8% of the vote against right-wing challenger Flavio Bolsonaro. His victory followed an intensive runoff campaign that combined youth mobilisation, a revamped social media strategy, opposition to the Bolsonaro family and a series of popular economic and welfare measures.

The 80-year-old incumbent had described his first-round campaign as the most "disorganized" in decades. Ahead of the runoff, he changed his digital outreach, sought support from young influencer politicians and encouraged supporters to take their campaign both online and onto the streets.

Here are four factors that ...