Would they risk a cover up? There must be quiet a few people working on this. And each one of them could blow the whistle. Also, what does the white house have to lose if it were a hack?
However our critical infrastructure needs to be secured in our country. This should be a major bipartisan issue too. Yet it seems like no one on either side of aisle is pushing for this. Just look at the recent attacks on power stations. If two people that want to rob some stores can take our power for thousands what can a foreign advisory hell bent on destroying the country do?
That's a fairly naive take. There are hundreds of thousands people (more?) working on classified programs to spy on citizens. The fact that leaks are so extremely rare that a Snowden is a once-in-a-generation type of event is plenty of evidence that very large groups of people do very successfully maintain massive cover-ups nearly 100% of the time.
Quite a lot of those have been linked to domestic extremism, and there's some distinctly partisan problems in even looking at that possibility.
I assume you are implying the right is doing the attacks here? A quick googling for attacks on infrastructure seems to mainly return cyber stuff. However most of the results on non cyber attacks are for multiple fires and train tracks that were sabotaged in past couple years in Washington state. The people that have been arrested for these attacks are not right wing, in fact for the most part they are from the left.