Bloomberg Politics has created an interactive map that visualizes the remarkably small group of Americans whose votes will determine which major party controls the Senate after Election Day. Here's the math:
* The population of America is about 319 million;
* about 230 million Americans are of age to vote.
* But only about 217 million of those within the right age range are eligible to vote, thanks to restrictions like felony ineligibility.
* About 65 percent of those who are eligible to vote are actually registered to vote,
* and midterm elections usually see only about 42 percent voter turnout from the pool of eligible votes — about 90 million in 2010.
* 34 states will have Senate elections this year, thanks to the rotating system of Senate terms,
* But only about eight states have hotly contested races that will decide whether the GOP retakes the Senate: Alaska, Arkansas, Colorado, Iowa, Louisiana, Kansas, New Hampshire, and North Carolina.
* Just 11 million people are likely to turn out to vote for Senate races in those states this November,
* which means that roughly 3.4 percent of the total population of the United States will decide who controls the Senate in 2015.
As Bloomberg points out, that's less than the population of Florida.