This will never again not be the case.
Every future presidency will be framed as having been stolen.
It started with Obama. We heard that a lot. He "stole" the presidency. The only way a candidate could "steal" a presidency is if he/she won by cheating. So you could say, Hillary was the illegitimate nominee of the Democratic party, because they conspired to work against Sanders. For Obama though, there were some fairly significant cases of voter fraud in 2012, but the numbers didn't come anywhere close to adding up to the margin of victory as far as we know. Despite the Russian interference, it does not appear that had an effect on this election. Most pundits, rightly, I think, believe that Comey had way more affect on the election results than what the Russians were doing. Also that Hillary did not campaign in the fly-over states near the end of the campaign, and it was in those states that she lost.