If it is a Republican, they will wait the night before the election to run it as they did with the Bush/drunk driving story so that there will be no time to answer it. That is how the MSM works.
The fact that this is mentioned now, it’s probably about Edwards or Obama. Unless one of the GOPers is playing with some guys privates, it wouldn’t have been mentioned.
That’s my opinion, too. They will wait to see if he becomes the pubbie nominee, if he does they’ll use it then to help the dem.
This is not exclusively an MSM tactic, it pretty universal among Dems and "progressives", and has been used a long time, at least 40 years that I know of.
It may have "started" in many local places, where it is very effective. My personal experience is in Marin County California, where the "dirt at the last minute" tactic was used with great success by Barbara Boxer when she was elected to the Board of Supervisors and subsequently to Congress.
Surprisingly, when she attempted to continue that tactic in DC, she was marginalized never to play a serious role again.
To a certain extent, Pelosi and Feinstein may have also dabbled in the practice.