Residents wait in line to pick up ballots at the courthouse in Waterloo, Iowa, when early voting in the state started on Sept. 27. Iowa's 3rd district race is one to watch: Democrats are voting early, but Republicans are likely to turn out on Nov. 6.
The percentage of people signed up for the mail-in voter list is slightly lower in rural areas. So this suburban House battle between Rep. Mike Coffman (R) and state Rep. Joe Miklosi (D) is ground zero for the early vote operation.
7. North Dakota Senate Early voting starts Oct. 22
Residents prefer to vote early via absentee ballot in the Peace Garden State, and the lax voting laws make the Senate race between Rep. Rick Berg (R) and former state Attorney General Heidi Heitkamp (D) all the more interesting.
North Dakota has no voter registration: Voters only have to show proof of residency, such as a utility bill, at the polls. To vote absentee, voters can sign an affidavit with their ballot starting Sept. 27.
The early vote is particularly important in North Dakota because of the small population. Operatives expect about 350,000 ballots to be cast in the Senate race.
8. Any California House race Early voting starts Oct. 8
Take your pick of about dozen competitive races in the state: Rep. Dan Lungren's (R) campaign in the 7th district, the open-seat race in the 26th district, or Rep. Brian Bilbray's (R) re-election in the 52nd district, to name a few.
Early and absentee voting will play a role in all of these races - but it will be most important in places with large minority populations. For example, Rep. Mary Bono Mack (R) is in a competitive race in a district where a quarter of the voting age population is Hispanic.
9. Florida's 18th district Early voting starts Oct. 27
Early voting is important in every competitive Florida House race because of the state's large absentee ballot and minority populations.
But early ballots matter especially in the 18th district: Rep. Allen West (R) is currently a slight favorite over businessman Patrick Murphy (D). Absentee ballot operations are key because of the large "snowbird" population north of West Palm Beach. There's a sense of urgency among Republicans to have these older voters cast their ballots early, even though these part-time residents don't typically head south for the winter until after Nov. 6.
10. Illinois' 11th district Early voting starts Oct. 22
The Land of Lincoln has made significant changes to its voting laws in recent cycles. The legislature passed a law to start early voting in 2005, and last cycle the state dropped its requirement for voters to give a reason to vote absentee.
The state features a few competitive House races around the Chicago suburbs - typically prime territory for early voting turnout. But this race between Rep. Judy Biggert (R) and former Rep. Bill Foster (D) could be particularly affected by the state's early voting law. There's a growing minority population around Aurora that makes the 11th fertile early vote territory.
Vice President Joe Biden waits to conduct a mock swearing-in ceremony with Sen. Brian Schatz, D-Hawaii, in the Capitol's Old Senate Chamber, December 2, 2014. Schatz was sworn in to serve the remainder of his term since he was appointed to the seat after Sen. Daniel Inouye, D-Hawaii, passed away.