Unfortunately, there is no obvious way to exactly determine what effect the Russian leaking of emails had on the actual results, although with Trump winning Pennsylvania, Michigan and Wisconsin (with a total of 46 Electoral College votes) in each case by 0.7% or less, it would have taken only a small effect to make Clinton the winner. However, there is far stronger evidence that James Comey's issuing a letter  less than three weeks before the election that he was reopening the investigation into Clinton's emails (without any knowledge of whether there was any new, relevant, evidence) had a decisive effect. Before the letter, the consensus of major opinion polls was that Clinton had a 6-6.5% lead in the popular vote but after the letter, in the lead up to the election, this edge dropped to 2-2.5%. Since the final result showed that Clinton had a 2.1% lead in the popular vote, the polls appear to have been quite accurate and that Comey's intervention swung the election to Trump.