When the polls close on election day, the contest between Obama and Romney comes down to these crucial battlegrounds

The campaign is nearing an end. The final polls are being conducted. Soon enough, we’ll all be sitting and watching actual votes being counted.

For election junkies like myself, we always have a lot of data in our minds. We know a state’s voting history and what to expect from it. What I’ve done here is try and put you inside the head of someone like me. I’ve laid out, as clearly as possible, what I believe are the key states in the presidential race on election night, along with key details on each state including closing times (note that no state will be called until the last closing time for a given state), polling average, voting history and the key swing counties in each state.

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The assumptions made here are pretty simple. We start with an electoral map where President Obama holds a 237 to 206 electoral vote lead. This leaves eight swing states listed below. You might notice that some of the peripheral swing states such as North Carolina and Pennsylvania are not listed. If either Obama carries North Carolina or Romney wins in Pennsylvania, this election is likely to be over very quickly. They are not swing states in my opinion.

So, here are write-ups on the key swing states in chronological order of poll closings.

Virginia (7pm ET)

Real Clear Politics average: Romney +0.5 points

2008 result: Obama won by 6.3pt

2004 result: Bush won by 8.2pt

Swing counties with 50k+ population (in every case, percentage points more Democratic than state in 2008): Henrico (+5.9)

No state better represents the old v the new south. The northern part of the state surrounding Washington, DC is filled with highly-educated Democratic supporters, while most of the rest of the state’s white population is Republican. Obama also benefits from a large African-American population in the south-east. Virginia had not voted for a Democrat for president since 1964 until it voted for Obama in 2008. The polls show the state to be dead-even, so expect this race to take hours for the networks to call as northern Virginia is usually the last to report.

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Ohio (7.30pm ET)

Real Clear Politics average: Obama +2.3pt

2008 result: Obama won by 4.6pt

2004 result: Bush won by 2.1pt

Swing counties with 50k+ population: Hamilton (+2.2), Lake (-3.7), Montgomery (+1.6), Portage (+4.4), Stark (+0.9), Wood (+2.5)

No Republican has ever won the presidency without winning Ohio. This year will likely not be an exception. Obama is buffered by a large African-American population surrounding Cleveland, as well as old conservative Democrats along the state’s eastern border. Romney benefits from evangelical support in the more rural areas in the western and southern sections of Ohio. Romney’s strength with white working-class voters has been slowed in Ohio because of Obama’s support of the auto bailout and Romney’s lack thereof. Obama holds a small lead in the polls: don’t expect the state to be called by the networks for at least four hours after closing.

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Florida (7pm ET for eastern part of state; 8pm ET for the west)

Real Clear Politics average: Romney +1.2pt

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2008 result: Obama won by 2.8pt

2004 result: Bush won by 5.0pt

Swing counties with 50k+ population: Duval (-0.9), Hernando (+0.7), Hillsborough (+4.4), Pasco (+0.8), Sarasota (-2.9), Volusia (+2.9)

George W Bush won the state by 537 votes and, with it, the White House in 2000. Much of the northern two-thirds of the state is filled with residents whose families have lived in Florida for generations. These folks are Romney’s strength, along with Cubans in Miami. Obama will do very well with a growing non-Cuban Hispanic population around Orlando, black voters and Jewish retirees in the southeast. Look at the I-4 corridor in the central part of the state from Orlando to Tampa: whoever wins the I-4 will likely win the state. Polls give Romney a slight edge, although it is too close to call.

New Hampshire (7pm ET for most of state; 8pm ET for a few bigger cities)

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Real Clear Politics average: Obama +2.0pt

2008 result: Obama won by 9.6pt

2004 result: Kerry won by 1.4pt

Swing counties with 50k+ population: Hillsborough (-5.9), Merrimack (+4.2)

New Hampshire was the only state to vote for George W Bush in 2000 and John Kerry in 2004. It supported Obama in 2008, but did a U-turn and voted three Republicans to the federal government in the 2010 midterms. The state is nearly all-white, yet it has a unique mix of old-time Libertarians, tax escapees from Massachusetts (note there’s no income or sales tax in New Hampshire) and social liberals on the state’s western edge. New Hampshire only has four electoral votes, but they could play a big role in a number of electoral scenarios. The race here is too close to call, with perhaps a slight edge to Obama.

Colorado (9pm ET)

Real Clear Politics average: Obama + 0.9pt

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2008 result: Obama won by 9.0pt

2004 result: Bush won by 4.7pt

Swing counties with 50k+ population: Arapahoe (+4.0), Jefferson (+0.1), Larimer (+0.8)

This state is ground zero for the newer parts of the Democratic formula to win, despite losing working-class whites. Latinos, along with a growing highly-educated white suburban population around Denver, have shifted this former Republican stronghold into a state where either party can win. Republicans still run strong in the exurbs of Weld and the strongly religious El Paso County, home to the Christian conservative group Focus on the Family. Jefferson County, which is the basis for the comedy South Park, is likely to mirror the state’s vote. Polling in the state indicates that the race is a true toss-up.

Wisconsin (9pm ET)

Real Clear Politics average: Obama +5.0pt

2008 result: Obama won by 13.9pt

2004 result: Kerry won by 0.4pt

Swing counties with 50k+ population: Kenosha (+4.2), Outagamie (-2.3), Racine (-6.7), Winnebago (-2.3)

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No state is perhaps more partisan than the Badger. It was here where a recall drive against the state’s controversial Republican governor failed in June. Each candidate is pretty much locked in, with 47% of the vote no matter what. Obama can count on Milwaukee with its black population, socially liberal whites around the University of Wisconsin and old-time Democrats in the west. Romney must crush in the Milwaukee suburbs, which are among the most conservative in the nation. The area around Green Bay in the northeast matches the word “swing” perfectly. If Romney doesn’t win Ohio, he must win here. Polls give Obama a small lead.

Iowa (10pm ET)

Real Clear Politics average: Obama +2.0pt

2008 result: Obama won by 9.4pt

2004 result: Bush won by 0.7pt

Swing counties with 50k+ population: Polk (+5.1), Scott (+5.0), Woodbury (-10.0)

This state is where the primary season begins, and it likes to keep Americans guessing. It’s a mix of old heartland liberals in the east and very conservative evangelicals in the west. This was one of only two states that voted for Al Gore in 2000 and George W Bush in 2004. No state has better mirrored the national vote since 1992 than Iowa. Early voting suggests a tight race, while polling gives Obama a small advantage. Obama won his first victory outside of Illinois here and would like to win where his national candidacy began. Iowa has historically not been decided until very late in the evening.

Nevada (10pm ET)

Real Clear Politics average: Obama +2.7pt

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2008 result: Obama won by 12.5pt

2004 result: Bush won by 2.6pt

Swing counties with 50k+ population: Washoe (+0.1)

There is perhaps no better example of the gaining influence of Latinos in the American south-west. Combined with Jewish retirees, blacks and white casino workers, Latinos form the Democratic base in and around Las Vegas. Democrats, led by Senate Majority leader Harry Reid, have been registering voters at an incredible pace. Mitt Romney is relying on a base in the rural areas, including a large Mormon population. Washoe County in the north-west is a swing county and usually votes with the winner. Early voting suggests that Obama will carry the state, with polling mostly agreeing: Obama will likely win Nevada by a small margin.

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