INDIANAPOLIS -- Monday is the deadline for Indiana residents who want to register for the historic May 6 primary election in which Indiana voters will play a role in determining who secures the Democratic presidential nomination.

It is also the first day registered voters can cast absentee ballots in person.

Secretary of State Todd Rokita said 51,000 new voters have registered in Indiana since the beginning of the year, not including thousands of registration forms filled out over the weekend and Monday morning.

Polling places are expected to be busy as Hoosiers choose candidates in a number of races, including the hotly contested contest between Sen. Barack Obama and Sen. Hillary Rodham Clinton.

The Marion County Clerk's Office anticipates a large number of college students will vote absentee.

Clerk Beth White said poll workers are being trained to handle crowds and extra voting machines will be prepared in some of the busiest precincts.

"We have been interacting with the presidential campaigns on the Democratic side in particular," White said. "They've been doing a registration drive, and then preparation to bring voters here. They want to encourage voters to vote early."

Absentee ballots are accepted through May 5.