It wasn't just Obama, though, pushing the presumptive Republican nominee to put the issue of his tax returns to rest.
Bain far from fading, Obama keeps after Romney
(Note: the superlink buttom fails to work. When clicks on it recent days, the page will break down. So I put the link directly)
To put an issue to rest is to settle it, so it is not "an issue" (not controvertial, not still talked about) any longer.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.