On the morning after the conclusion of the Democratic National Convention two things happened: Mitt Romney’s campaign announced an eight-state ad buy, and the national election map got a whole lot smaller.

Not that anyone should be surprised.

Actually, Romney’s running not just an ad, but 15 separate spots in the following swing states: Colorado, Florida, Iowa, Nevada, New Hampshire, North Carolina, Ohio and Virginia (interestingly, Paul Ryan’s Wisconsin didn’t make the first cut). As if to reinforce the point, Romney spent the weekend in Iowa, New Hampshire and Virginia.

And then, over the weekend, Romney added Wisconsin to the equation, buying ad-time in that state as well for a total of 16 spots running (nearly) coast to coast.

What does this mean for the “national” election?

Let’s suppose you’re a Californian, casting a ballot in a state that has 55 electoral votes – two more than Colorado (9), Iowa (6), Nevada (6), New Hampshire (4), North Carolina (15) and Virginia (13). Your best chance of seeing Romney? Either if the candidate pops into the Golden State for a fundraiser, or if Romney swings by the family beach house in La Jolla to drop off some laundry. The same goes for New York, Illinois and Texas – all big states that lack for competitiveness and therefore lack for either party’s interest at this point in the general election.

Welcome to the incredible shrinking election – a 50-state contest in which the two parties are competing earnestly, truth be told, less than 10 swing states.

And here’s where you can pull out your campaign abacus and start calculating where the electoral votes will divide.

For the sake of argument, let’s put the aforementioned nine swing states that have drawn Romney’s interest in the undecided column, and assign the remaining 41 states (plus D.C.) into red and blue columns. By my count, Obama is ahead 237-191, with 110 electoral votes up for grabs (I’m putting Indiana back in the GOP column, as its an ordinarily Republican state that Obama carried it by a whisker in 2008).

Now let’s add North Carolina to Romney’s column (a survey released last week has Obama trailing by 4% and there’s growing consensus among campaign observers that the Democrats aren’t counting on a repeat of the razor-thin victory there in 2008). The readjusted total: Obama 237, Romney 206, 95 undecided.

So where do the two camps go from there? Look to Florida, Ohio and Virginia. If Obama wins all three, he’s at 297 electoral votes. Game over. If Romney sweeps all three, he’s at 266 – any one more undecided state will put him over the top.

But if the three state split? Here’s where life gets complicated . . . for Romney, as he's trying to take away state Obama carried four years ago.

Hypothetically, what if Romney wins Florida and Ohio, but not Virginia? That puts him at 253 electoral votes. Romney would need at least two smaller states to make up for the loss. But if he gets only Iowa and Nevada, to go along with New Hampshire: he’s stuck at 269 electoral votes.

Remember this cliffhanger scenario: among the swing states, Obama carries Colorado, Virginia and Wisconsin; Romney carries Florida, Iowa, Nevada, New Hampshire, North Carolina and Ohio. It’s a 269-all deadlock and the presidential election heads to the U.S. House of Representatives.

One other what-if and it’s a big one: Romney’s chances of taking Ohio. In late August, a Columbia Dispatch poll had Romney ahead by 0.22% (the narrowest margin ever – amere 2 votes out of more than 1,730 cast for president in the mail poll), with a healthy 10% undecided.

To say the state’s pivotal would be an understatement. Ohioans have sided with the winning candidate in the last 12 presidential elections (Richard Nixon carried it in 1960). What’s Romney’s roadmap should he prove unable to turn Ohio red in November? If he carried the other eight swing state, he finishes with 283 electoral – 13 to spare. Take away Wisconsin and its electoral votes and he’s still over the top. But take away New Hampshire as well and we’re back to that 269-all scenario.

About that tiebreaker: one of the overlooked aspects of the 2010 congressional elections was the changing of hands not just of the Speaker’s gavel, but control of the so-called “electoral backstop”. Prior to the last midterm, Democrats had a 33-16 lead among delegations. The landslide changed that: Republicans gained control of 33 delegations.

Why the significance of that switch? If the presidential election goes to the House (it’s only happened before in 1800 and 1824), the outcome’s decided not by members but instead by the 50 delegations – each state getting a single vote.

In which case, the election will have shrunk even more – from 110 electoral votes to 50 votes on Capitol Hill.

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