BERLIN — Gay rights have quickly emerged in Germany as a campaign issue in this parliamentary election year, with Chancellor Angela Merkel’s conservative Christian Democrats struggling to catch up to changing attitudes among voters on issues like gay marriage and adoption.

The debate here was given new impetus by a decision earlier this month by the Federal Constitutional Court, which ruled that gays and lesbians should be allowed to adopt children already adopted by their partners. The next battle, over tax benefits for civil unions, has already begun.

“The decision to put civil unions and marriage on level footing needs a big push,” Justice Minister Sabine Leutheusser-Schnarrenberger told the news Web site Spiegel Online on Wednesday.

The issue is particularly contentious for Ms. Merkel’s Christian Democratic Union, which has tried to balance a conservative, traditional family-values approach favored by the party’s older voters with appealing to younger voters who support gay rights in greater numbers.