“WE THOUGHT this would be an eight-month pregnancy but in the end it’s going to the full term,” joked Michelle Bachelet, a paediatrician, on November 17th as she celebrated a bittersweet triumph that took her centre-left New Majority coalition tantalisingly close to the presidency. Having won 47% of the vote, nearly twice as much as her closest rival, Evelyn Matthei of the ruling centre-right Alliance (25%), she now faces a run-off on December 15th.

Ms Matthei will struggle to win the support of the 28% of voters who backed the losing candidates, a clutch of populists and leftists. In the first presidential election in which voting was voluntary, only 49% bothered. So Ms Matthei has decided to try and rouse non-voters with “a message of moderation”.

That plays on fears in some quarters that Ms Bachelet, Chile’s president in 2006-10, has swung further left, endorsing the demands of a student movement which wants education to be free to users, and promising tax increases and a new constitution. The New Majority, which unlike the previous centre-left Concertación coalition includes the Communist Party, won a majority in both houses of Congress. It will have 68 seats in the 120-seat lower house and 21 of the 38 Senate seats.

The centre-right Alliance did better than Ms Matthei. Even so, the biggest loser was her Independent Democratic Union, the more conservative of the grouping’s two parties and closely identified with the dictatorship of General Augusto Pinochet. It lost ten lower-house seats, though it still has 28 and remains the largest single party in Congress.

Ms Bachelet, assuming she wins, will have the votes in Congress for tax and probably education reform. But to secure the two-thirds needed to make big changes to the constitution or the voting system, as she wants to, she would have to gain the Alliance’s support.

That may prompt tensions within the New Majority. The far left and the student leaders who have dogged the outgoing government of Sebastián Piñera did well. The Communist Party doubled its seats in the lower house to six. Four former leaders of the student movement, including Camila Vallejo, a geography student who became a media celebrity in 2011, were elected to Congress. Several experienced and moderate Concertación politicians lost their seats.

Everything suggests that the birth of Ms Bachelet’s second presidency will be straightforward next month. But the baby is already preparing to kick hard against its mother.