Republicans from the Republican National Committee to the state and local levels are trying to rewind it and get their voters to request postal ballots, but they are working against a strong force: Donald Trump. Senate Majority Leader Mitch McConnell and others stood up to Trump to distinguish between "universal" postal voting and postal voting, where each voter must specifically request a postal vote, but it's too little, too late, too confusing. Especially as Trump continued his attacks on postal voting during the debate, one of his biggest platforms in the campaign.
Republicans are planning a multi-faceted effort, trying to get their voters to send ballots, but also working for a large turnout on election day, trying to get as many Democratic votes as possible. Much of this effort will come after the election, when the votes are counted, and will come when Trump tries to sow doubts about the validity of the votes, the count, and the election – and most importantly, the loss he's so evident expected to come.
According to University of Florida political scientist Michael McDonald, one in five votes cast so far in North Carolina and Georgia is from people who did not vote in 2016, and in some states almost 10% of the 2016 votes have been cast as is their custom, Republicans do not consider it a good thing that the people should be ready to vote or that the people vote after the last election. This is a very frightening emergency for Republicans.
Trump's attacks on postal voting make it more likely that not only he but also Republicans will lose in November. However, he won't quit because he is serious about refusing to give up power when he loses. Victory in the elections is no longer his priority, nor does he care about the Senate, House, or other Republican candidates.