Merkel has previously argued against same-sex marriage. She criticized Schroder's anti-US position in a Washington Post editorial piece in 2003, stating that she backed military action against Saddam Hussein as a last resort.
And, finally, she said her piece: "I would like to lead the discussion into a situation of a question of conscience, instead of me having to push something through with a majority resolution".
Support for same-sex marriage in Germany is widespread.
The poll has a margin of error of plus or minus 2.5 percentage points. Same-sex couples may enter into a civil union but can not marry, and they are not allowed to jointly adopt children. "The FDP firmly believes that all humans, regardless of gender, deserve the same rights as long as they take responsibility for one another".
Gay rights have always been a controversial issue within the CDU and its more conservative Bavarian sister party, the Christian Social Union (CSU).
Their leader, former European Parliament President Martin Schulz, has made a decision to run as a social justice warrior, proposing to raise taxes on the rich.
"We don't know whether we can rely on the United States, but we know very well that we can no longer rely on an erratic President Donald Trump", Schulz said, as quoted by Bloomberg.
Speaking at an event on Monday, Merkel was asked by a gay man when he would be allowed to refer to his registered partner as his husband.
The Federal Anti-Discrimination Agency of Germany backed Ms. Merkel's change in approach.
Axel Hochrein, a board member of the Lesbian and Gay Federation in Germany, cheered the chancellor's statement but said it was long overdue.
He also laid down gay marriage as a condition for any future coalition involving the SPD.
In the interview with the editor of Brigitte, Merkel spoke about a range of personal and political issues.
The chances of denying Dr Merkel a fourth term look slim for the SPD, which is the junior partner in her right-left coalition. "With three possible coalition partners now declaring that the opening of marriage must be in the coalition contract, perhaps she wants to solve the problem before it appears after the election".
The rival Social Democrats (SPD) were unchanged at 23 percent, while the pro-environment Greens gained 1 percentage point to 9 percent and the anti-immigrant Alternative for Germany (AfD) party was unchanged at 7 percent, Forsa said.