Story highlights Democrats boost voter advantage in Florida, Nevada and Colorado

The voter rolls change from month to month

(CNN) Democrats have expanded their voter registration leads in Florida, Nevada and Colorado, providing a boost for Hillary Clinton in those key battleground states.

Republicans maintained their edge in Iowa, and improved their position in Pennsylvania, but they still lag behind Democrats there by more than 900,000 registered voters.

In Florida, Democrats added more than 25,000 more voters to the rolls than Republicans in the past month, according to new data from the Florida Department of State. The overall Democratic edge is now almost 300,000 --- lower than 2012, but higher than it was this summer.

The registration deadline in Florida was delayed for a week by a federal judge after Hurricane Matthew forced millions to evacuate and displaced many from their homes. Tuesday was the last day to register.

Election officials in Colorado started mailing out ballots to residents Monday, the first presidential election in the state's history where all registered voters automatically get a ballot in the mail.

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