Here's the problem: this administration promised to be transparent. The implication there is that previous administrations weren't, and that this one would be better than them. Stonewalling and refusing to investigate a criminal allegation raised by a member of their own party is problematic to say the least.
Impeachment is obviously a non-starter given the Democratic majorities in both chambers. However, this could certainly lead to somebody getting fired/resigning and/or being prosecuted. Depending on exactly who authorized the action, it could be pretty high up the ranks of the administration.
And I'm not surprised that Rover chose to focus on the inflammatory portions of the article rather than the important parts I mentioned (the actual statute in play and the fact that Sestak has been making this claim for months now). I don't care about a bunch of blowhards spouting off about impeachment; I do care about the applicable law to this situation and whether or not that law was broken. It does not reflect well on this administration.