I'm not so sure about that. In order for the Articles of Impeachment to be invoked, there must be evidence of high crimes and misdemeanors. An affair does not qualify.
It was different in the case of Bill Clinton though, for the charge of high crimes and misdemeanors was not on the basis of his affair with Monica Lewinsky, but rather on the charge of perjury in that he lied about it, and obstuction of justice regarding the Paul Jones case.
There is absolutely a discussion to be had if those two charges qualify as "high crimes and misdemeanors" but make no mistake about it. The charges were over perjury and obstruction of justice, not the affair itself.
In Trump's case, giving money to keep an affair quiet is certainly questionable ethical behavior, but it does not qualify as high crimes and misdemeanors. If Obama had done the same thing, I don't think Republican's would have had a case against him for that same reason.
I'm not trying to take a side here, but rather to call this issue like I see it.