This is an indirect answer--not answering the style question directly, but it's the practical answer in general, so it's worth mentioning.
I find it extremely rare to need to write multi-line conditionals. There are two factors to this:
Grepping through my recent projects, around 12kloc, there's only one conditional long enough that it needed to be wrapped; the issue simply very rarely arises. If you do need to do this, then as nosklo says, indent it separately--as you noticed, indenting it to the same level as the block beneath it is confusing and hard to read.