This is President Obama taking a swing. He is not a swing voter. (AP Photo/Steven Senne)

The swing voter is increasingly an endangered species.

According to a new poll from Democratic pollster Democracy Corps of a dozen states hosting the most competitive Senate races, only about one in 12 people who favor one side or the other is a bona fide swing voter in the upcoming election.

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The poll shows just 7 percent of people who favor the Democratic candidate and 8 percent of people who favor the Republican candidate say there's even a "fair chance" they will change their minds.

That, though, doesn't include undecided voters, who number 8 percent, according to the poll. But even if you assume they'll definitely wind up voting, that's only about 15 percent of people in key races (about one in six) who are genuinely persuadable. The rest say there's no more than a "small chance" that their vote is in play.

This, at the very least, is more than the 2012 presidential election. As of July 2012, just 6 percent of Americans said there was a "good chance" they would change their minds about the upcoming election, according to Washington Post-ABC News polling. Another 13 percent said it was possible but unlikely that they could change their minds.

The terms in that poll and this new one aren't the same, so it's not a direct comparison. But it seems that there are at least more swing voters in 2014 than in 2012.

That makes sense. A presidential race is defined rather early and is more partisan, because people get to know the candidates much earlier. In a midterm, it's fair to assume many or most voters haven't done a whole lot of homework on the candidate they'll be voting for or against come Nov. 4. And even then, just one in six Americans are up for grabs.

Which is why both side are increasingly focusing so intently on turning out their bases. It's great to win over swing voters, but the base is an increasingly important part of the winning calculus -- as this poll shows.