Republican Donald Trump and Democrat Hillary Clinton's campaigns have prepared their get-out-the-vote efforts for more than a year. On Monday, when early in-person voting for the Nov. 8 election begins, they'll face their biggest test yet.

Almost half of the Georgia ballots cast in the 2012 presidential race – nearly 2 million – were cast ahead of Election Day. With that total expected to rise this year, both campaigns plan to capitalize on the early-voting launch.

Democrats plan a rally Monday at South DeKalb Mall, a "Millennial March" in downtown Atlanta led by U.S. Rep. John Lewis, and a "Forward Together" bus tour in Augusta and Athens featuring former Rep. John Barrow and Augusta Mayor Hardie Davis.

Trump's campaign brought in Donald Trump Jr., the New York businessman's son, on Friday to urge Republicans to cast their ballots early.  And the Millennials for Trump group held a rally Sunday at Georgia State University featuring Brietbart News editor Milo Yiannopoulos trying to rev up young supporters.

Hundreds of thousands of voters in other states have already cast ballots – including at least 8,000 absentee ballots that have already been tallied in Georgia – and the early signs bode well for Clinton. Democrats are cutting into Republican early-voting advantages in North Carolina and Florida – both pivotal to Trump's November chances.

Trump's camp points to encouraging signs in Iowa, where GOP absentee ballot requests outpace the Democrats, and Ohio, where Democrats aren't keeping pace with their 2012 early-vote performance.

The battle over the early vote is becoming more important every cycle as more states – and more voters – embrace the chance to cast their ballot weeks before Election Day.

Georgia is one of 37 U.S. states that allow early voting in some form or another and nationwide about 42 million people – or nearly one-third of voters – voted in 2012 before Election Day. Some analysts believe that total could near 40 percent this year.