Over the past two years, eight states have changed the dates of their primary elections to accommodate military voters, while 38 states plus the capital city have established rules or laws that go beyond the federal requirement to provide ballots to overseas voters at least 45 days before elections.

And every state now allows blank ballots to be sent electronically, either by fax, email or over the Internet.

David Becker, who directs Pew's elections initiative, said the report reflects substantial improvements, but that more work must be done to fulfill what he called a moral imperative to ensure military members and their families are able to vote consistently. He said the center will be observing the November 2012 elections for evidence of how the new rules are working in practice.