Dem
51
GOP
49
Republicans in recent years have vigorously opposed voting by mail as potentially fraudulent even though historically it has mostly been seniors who vote by mail and they skew Republican. This brings up the question of whether voting by absentee ballot helps one party more than the other. Recent studies suggest two things about absentee voting. First, it boosts turnout. Second it doesn't seem to give either party an advantage over the other.
One study of the 2020 election in particular showed that although 58% of the Democrats voted by mail and only 32% of Republicans voted by mail, on the whole, over the whole country, voting by mail did not lead to any partisan advantage. What studies can do is compare the Democrats' fraction of the vote in counties and states that have vote by mail with comparable ones that do not. If there is no significant difference, then the conclusion is that if voting by mail is not possible, then Democrats don't say "I'm not going to vote," instead they vote in person and the net effect isn't very much.
The study did observe a small difference between states with no-excuse vote by mail and states where some kind of excuse was needed to get an absentee ballot (like a doctor's note). The Democrats had a small advantage in the no-excuse states.
A bigger effect, however, is how much effort the parties put into voter outreach. When absentee-ballot applications were mailed to voters without their asking for them, turnout went up. Democrats have understood this for a long time, but now Republicans in a number of states are catching on and also encouraging their voters to vote by mail. If both parties do this equally, the effects are likely to cancel out and the main effect will be to boost turnout on both sides (and result in shorter lines at the polls).
In particular, in Virginia, Glenn Youngkin is actively pursuing a vote-by-mail strategy for the General Assembly elections, something Republicans have rarely done in the past. One problem he has, though, is that Donald Trump is against voting by mail and is telling his supporters not to do it. This means that Youngkin doesn't only have to get the mechanics right, he also has to convince voters that their absentee ballots will not be tossed into the shredder by Democratic election workers. That may be difficult. But long term, as the Republicans come to realize that absentee voting doesn't hurt them, they may drop all resistance to it and it may become much more common. (V)