Voters who have already cast their general election ballots tend to be from Democratic parts of the state.

Minnesotans from strongly Democratic areas or counties that lean toward Democrats cast about half of the absentee and mail ballots so far, according to a Star Tribune analysis of the state data on accepted absentee ballots as of Oct. 6.

Only about a third of the accepted ballots have come from areas that are strongly Republican or have leaned that way in the past decade's worth of elections. The rest are from counties that swing between Democrats and Republicans.

In recent years, Democrats have heavily encouraged voters to cast absentee ballots, if they were unable to get the polls. Before this year's August primary, which featured a heated Republican race for governor, more ballots came from Democratic areas than Republican ones.

This year, for the first time, Minnesotans are permitted to cast absentee ballots without needing a specific excuse for not voting on Election Day. That absentee ballot period began Sept. 19.

Since then, voters from the heavily Democratic Fourth and Fifth Congressional Districts have cast a combined 28 percent of the total ballots already accepted. Voters in the heavily Republican Sixth Congressional District have cast just 8.5 percent, the lowest congressional percentage.

It's the voters in the northern Eighth Congressional District who have really warmed to the absentee ballots. They have cast more than 4,000 votes, or 20 percent of the total — more than any other congressional district.

This year, the Eighth District features a nationally watched House race between Democratic U.S. Rep. Rick Nolan and Republican challenger Stewart Mills.

An analysis of the ballots from Eighth District shows that those who have already voted are far more likely to come from strong Democratic areas than strong Republican ones.

Fully a third of the ballots from that district came from cities and towns that voted for former U.S. Rep. Jim Oberstar when he lost to Republican Chip Cravaack in 2010 and voted for Nolan over Cravaack in 2012. Only 4 percent of the total Eighth District votes have come from areas that always vote Republican in congressional races.

But swing voters in the northern district also have been using the vote-early option.

A little more than 30 percent of the total absentee ballots from the Eighth have come from areas that shifted from Oberstar to Cravaack and then stayed with Cravaack in 2012.

Of the nearly 20,000 ballots that have come from across the state, older voters have cast the most. The analysis of individual voters' information shows 65 percent of voters who already have had their ballots counted are age 65 or older.

It also shows that baby boomers like to vote early. Forty percent of the ballots already accepted came from people born between 1945 and 1964.

Last week, the Secretary of State's office reported that more than 50,000 absentee ballots had already been sent out and election officials had already accepted more back than they had at this point in 2010.

Rachel E. Stassen-Berger • Twitter: @rachelsb

Glenn Howatt • Twitter: @GlennHowatt