The winner of the U.S. presidential election will be determined by about 17 swing counties, with a total of about 500,000 swing voters between them.

The American public has heard that 12 swing states will determine who will be the next president. But a book, Presidential Swing States: Why Only Ten Matter, by Hamline University Professor David Schultz, who also edits the Journal of Public Affairs Education, predicts a very small number of America’s 3,142 counties and county equivalents will tip the balance.

In Ohio, it’s Hamilton County, home to Cincinnati;

In Pennsylvania, the key counties are Bucks and Chester Counties, to the north and south of Philadelphia; along with Lackawanna and Luzerne Counties, straddling Scranton and Wilkes Barre in its western interior;

In Florida, it’s Hillsborough and Pinellas Counties, surrounding Tampa and St. Petersburg;

In Wisconsin, the keys are Brown County and Winnebago County near Green Bay; plus Racine County to the south near Chicago suburbs;

In Iowa, it’s rural tiny Bremer County;

In New Hampshire, it’s inland Hillsborough Township, on the Massachusetts border;

In Nevada it is Clark County, home of Las Vegas;

In Virginia, it’s Prince William County, outside Washington D.C.;

In North Carolina, it’s Wake County, which encompasses Raleigh and Durham; and

In New Mexico, it’s Bernalillo County, along with Albuquerque and Dona Ana County near Las Cruces.

(Many of these overlap with the twelve counties identified by Ed Morrissey in a similar book, Going Red: The Two Million Voters Who Will Elect the Next President–and How Conservatives Can Win Them, published in 2015.)

According to Schultz, “These seem to be the counties within the swing states where the candidates go.” He added, “They view them as battlegrounds. They seem to be pretty good bellwethers, in the sense of predictors of how that state is going to vote… Even if they appear blue or red, there’s a question of how great the turnout will be.”

The group of counties determined who won the election in 2012 by giving 2,485,793 votes to Barack Obama, compared to 2,106,985 votes for Mitt Romney. That means that just 189,404 voters in a nation of 319 million people determined the winner in 2012.

Schultz says the counties all sit between reliable Republican “red” and Democrat “blue” voter strongholds. The voters in these counties are suburban and experiencing major demographic shifts, including young and better-educated people moving in; and some are quite racially diverse.

Schultz says, “What we are seeing in these counties, at least right now, is relatively balanced, in terms of Republicans and Democrats.” But he adds, “We have a small portion of the population of these counties that are going to be the swing voter. When I say swing voter, I don’t necessarily mean swinging from Democrat to Republican. They might be swinging in to vote, or swinging out from voting.”