Climate change has vaulted to near the top of voters’ concerns in a Europe plagued by record-high temperatures. Traditional social democratic parties are collapsing as younger voters seek new allegiances and an antidote to the nationalist far right.

The upshot: The Greens will have roughly the same influence in the European Parliament as the far-right populists led by Italy’s interior minister, Matteo Salvini. Like the populists, green parties are networking across the Continent, coordinating campaigns and holding joint party conferences.

The challenge: The Greens have become enemy No. 1 for far-right populists and others who cast their policies as part of an elite agenda that hurts ordinary people.