There are two different situations. One is the election level. I don't think traditional conservatives would vote for a left candidate, because the conservative candidate is gay or lesbian. Indeed I think it is an advantage for any candidate to be homosexual, except the candidate is from 'Die Linke'. It is like moving left without really moving left on any issues. Merkel had as well an advantage because she was a woman in 2005 in the general election, because feminists have voted for her without agreeing with her on issues.

The other is an inner party decision. There a heterosexual candidate has clearly an advantage in conservative circles against a homosexual one. This was the case for Schavan.

Der Amerikaner ist die Orchidee unter den Menschen
Volker Pispers