Nah, someone being a legit threat makes them -necessary- to talk about. Your line of thought would likely be "If they ignore a serious threat, they won't gain traction due to lack of coverage", yes?
The problem is that it doesn't really work that way. The left doesn't have a monopoly on news. Leaving aside the every present word-of-mouth, you have political campaign events, right-leaning news sites and outlets, and the ever-present internet and radio news sources. Put simply, a good candidate WILL be known eventually. So why not ignore it until then? Well, because it would let them -entrench-, locking down the right-wing vote in its entirety. And with it locked down they would have absolute free reign to begin their sales pitch to independents.
Ironically, ignoring them would allow them to create an unassailable position of strength.