 In this capacity, she made headlines when she voted against her party's line and supported 2013 legislation introducing same-sex marriage in France.She also wrote a 2018 report about congestion pricing in London and Stockholm, which formed the basis for legislation making it easier for cities to introduce congestion pricing in a bid to reduce traffic jams and air pollution.In the Republicans’ 2016 presidential primaries, Keller endorsed Alain Juppé as the party’s candidate for the office of President of France.