Answer:
The voter participation rate would most likely increase
Step-by-step explanation:
Some voters do not vote out of pure laziness. They do not want to leave their houses to cast a ballot so they abstain from voting. Mail-in ballots are easier to cast because they can be done well in advance of the voting day. The ballot is sent by mail to registered voters who expressed their desire to vote this way. The voters fill in the ballot and than they return it by mail.
Even more effective way to guarantee more votes would be by email ballots, the voters would not have to leave their house in order to cast their vote.