The laws are designed to target latinos, blacks, college students and the disadvantaged (the poor and disabled). As a whole, these groups go democratic about 70-80% of the time (blacks vote democratic a little more, college students a little less, but overall that is about the ratio, maybe 3-1).
So that is 2 net democratic votes for every 4 votes cast. So if that is 2% of the electorate, that is a 1% net gain for the republicans.