Germany has allowed registered life partnerships for same-sex couples since 2001, initially with far fewer rights than married couples enjoyed.
Germany looked set on Friday to join more than a dozen other European countries - including the United Kingdom and the Republic of Ireland - in allowing gay couples to Wednesday. Though Merkel herself probably didn't intend for it to happen so quickly and voted against the measure, it dispatched the issue before election campaigning really started. He's been fighting for same-sex marriage for his entire political career.
The delay, says Markus Ulrich, spokesman for the Lesbian and Gay Federation in Germany, is down to Angela Merkel's ruling Christian Democratic Union.
Her seemingly inconsequential vote encapsulates some of the opposing forces tugging at Merkel, said Robert Beachy, the author of "Gay Berlin: Birthplace of a Modern Identity". She said she believes the German constitution views marriage as being between a man and a woman.
In contrast, same-sex marriage has proven to be a more hard challenge for the chancellor, as many members of her party remain staunchly opposed to it even as most Germans support marriage equality.
She told the editor of a German magazine that she recently had dinner with a lesbian couple who are raising eight foster children.
"Let's see what the future brings, but as we saw in other countries, if there is gender equality people are more aware that people love people and that has nothing to do with their sex or gender".
That red line would have been challenged sooner rather than later.
The gay marriage bill, a last-minute addition in parliament's last session before the summer break, was backed by nearly every party in the lower house.
All of Ms Merkel's potential coalition partners after the September 4 election, including the centre-left Social Democrats of her challenger Martin Schulz, have been calling for same-sex marriage to be legalised.
Friday's historic conscience vote was the result of a rapid series of events that saw the CDU's longstanding opposition to marriage equality effectively unravel within a week. More than a quarter of CDU lawmakers voted for the laws. But she also said she hoped the passing of the bill would lead to more "social cohesion and peace".