The polls were off by miles, but in the other direction from the alleged fraud; Democratic candidates received fewer votes and Republican candidates more than would have been predicted by polls.
There have, however, been very few claims of fraud benefiting Republican candidates, because this is mostly explained by high turnout by Republican voters due to strong personal support for Trump in a segment of the party that historically has low turnout. This is illustrated by improved performance by Democrats in runoff elections where Trump was no longer on the ballot.