The question is a strawman since ‘interfere’ is not defined.
Is trying to access secure networks and gather intel considered ‘interfering’? That’s what the NSA does for a living, they even record the private phone calls of the leaders of our allies.
Is donating money to political groups that favor one candidate considering interfering? This is a common occurrence here, and I believe the US does it with public funds in foreign countries.
I also know the CIA has operated political polling firms in foreign countries where the ‘surveys’ were used to persuade candidates to run for a specific office or take certain policy positions. The CIA has also managed the press abroad to push positions favorable to the US.
I’d say all the above is fair game. I don’t like it, but it’s also unavoidable.
What’s not acceptable is if a foreign govt is effectively stuffing ballot boxes and perverting the vote of people entitled to vote.
With Russia, I’ve seen not evidence of tampering with the actual election. We don’t even have evidence they leaked all those true but damaging emails that hurt Hillary.