CNN chief political correspondent Candy Crowley: Virginia suburbs and I-4 corridor
The first thing I'll watch is the exit polls to see who's voting and where -- in particular, heavy Latino turnout in Colorado, Nevada, Virginia and Florida could indicate Obama wins those states.
Then, it's Virginia, Florida and Ohio.
I'll watch the Virginia suburbs of Washington, particularly the female vote. Romney won't win here, but he has to hold down Obama's numbers while running up his own score in the rural area. Romney has to win Virginia.
Florida is all about the Interstate 4 corridor. North of it votes Republican; south of it votes Democratic. The I-4 corridor decides.
Everyone will tell you to watch Lake, Stark and Hamilton counties in Ohio. There are good reasons to watch all of them, reasons no doubt delineated by my colleagues. But for me, it's all about Ottawa County, which has correctly picked the presidential winner in Ohio since 1944. That's a better record than pollsters. I'll watch Ottawa.
CNN political reporter Peter Hamby: How goes Pasco?
Polls begin to close in Florida at 7 p.m. ET, and a handful of counties will report their absentee and early vote tallies immediately.
Once that happens, political pros in Florida will be anxiously refreshing election board websites in a handful of those counties -- Pinellas, Duval, Orange -- in search of early clues about which way the state is trending.
One of them is Pasco County, outside of Tampa. Officials there are diligent about posting returns as quickly as possible. The county has a slight Republican tilt, but Obama won the early and absentee vote there in 2008 despite losing the county on election night. For Democrats, it was a promising sign that Obama was well on his way to being competitive statewide, even in GOP-leaning areas.
In 2004, George W. Bush beat John Kerry in the Pasco early/absentee vote by 8 points. Bush ended up winning the county by 10 points. In a shift four years later, Obama beat John McCain by 5 points in the early absentee vote. He ultimately lost the county -- but only by 3.5 points, thanks to the votes the campaign banked early.
If Obama is losing Pasco by more than that Bush/Kerry margin by the time the first returns are posted, it could be a tough night for Obama in Florida.
"If you are looking for good news for Romney out of Pasco, if they have a 10- to 12-point lead in the absentee and early vote, that probably portends that they are going to have a really good night in suburban counties," said one top Florida Democrat.
CNN chief national correspondent John King: The suburban vote and who votes in the swing states
A narrow and then a more global point:
-- Watch the vote in the suburbs around Cleveland and Columbus, Ohio, and in northern Virginia. These are two early-closing states; if Romney is holding his own in the suburbs, we have a competitive night. If not, it could be effectively over before we get to the Central Time zone.
-- Who votes determines who wins: The composition of the electorate in the swing states is the first and best clue. Does the electorate look like 2008?
If so, then Obama is likely on a path to victory. But if the percentage of African-American, Latino and younger voters is down just a bit -- and the electorate looks, say, more like the 2004 presidential election -- then Romney has a shot.
CNN political director Mark Preston: What happens afterward?
It goes without saying that we are all looking at turnout in the key battleground states -- can Romney and Obama get their respective bases to show up at the polls and at the same time, convincing the independent voters to vote for them today?
What is piquing my interest is not only what happens in the next few hours but what will be the political climate for the next president-elect. Washington is already polarized and there are great challenges facing Congress before the end of the year.
Whoever wins the presidency and the parties that control the House and the Senate need to put the bitterness of this election behind them and work together.
The big question: Can they do that?
CNN political editor Paul Steinhauser: Can Romney broaden the electoral map?
This election will be won or lost in the battleground states. Or will it?