It's unclear who leaked to the media that the Broncos are interested in Peyton Manning -- let's accept it on its face that it is true.
That would make Denver the only team among the dozen or so angling for Manning who (a) already have an entirely capable incumbent QB, and (b) made the playoffs last year with an incumbent QB.
People ask why I think John Elway is disingenuous and why I think the media totally mis-read Elway's "supportive" quotes of Tebow, and it's things like this. The Broncos don't need Manning -- they have a starting QB who got them to the playoffs under some severely limited conditions.
Beyond that, the Broncos have virtually no shot at Manning -- he doesn't want to play for them and there are plenty of other teams he would rather play for (and would be thrilled to bid up to get him). So I'm not sure I see the point in floating the idea they would want him.
All it does is (continue to) undermine Tebow.
(This topic is totally aggravating, and yet it's still probably preferable to talking about whether Tebow is dating Taylor Swift, the discussion of which you'll notice has been absent from this site.)