Right before the election is far more dangerous. Fake or out-of-context portions will cause immediate outrage and take days/weeks to research and explain (and the French campaign blackout means the campaign can't explain until after the election).

As an example, 538 makes a compelling argument that the Comey letter - later found to be essentially a false alarm, but after the damage was done - influenced the US election. https://fivethirtyeight.com/features/the-comey-letter-probab...