How Big a Margin is Too Big to Make Up?

In yesterday's New York Times, John Harwood laid out the history of presidential comebacks from late polling deficits, but that isn't really what I'm after here. Reagan is the only candidate who mounted such a turnaround when he unseated Jimmy Carter in 1980. The question I'm asking, though, is one I've been thinking about for the better part of two weeks because of an anonymous comment I got. [Granted, I did the leg work for this a couple of weekends ago, but I'm just now getting to it. It may not be as pertinent now with Obama seemingly comfortably ahead, but I'll press on regardless. More information is better than less in my estimation.] Here's the idea:

"Here are the margins that Bush won these states in 2004:
Ohio 2.1%
Nevada 2.6
Colorado 4.7
Florida 5.0
Virginia 8.2

It's hard for me to believe that Virginia would change 8.3% in one direction(to Obama) therefor don't be surprised if/when McCain starts polling better in Virginia."

I'll have to say, 8.3% does sound like a lot to make up in just four short years; especially in a reliably red state like Virginia. So at first glance, this sounds like an entirely reasonable hypothesis. But it is never good enough for me to simply take someone's word for it. The one question that arises from this is, 8.3% is a lot, but compared to what? What is the typical swing from one party to the other from election to election? Oh, I'm glad you asked. Let's have a look.

First off, I looked at all the swings from 1984-2004. That'll give us a total of five transitions and enough variation in the types of elections to give us a decent idea of what is business as usual in terms of these swings. There are several combinations here but two main hypotheses emerge from the electoral shifts we have witnessed over the last five cycles:

H1: Swings from one party to the other are likely to be larger in elections where the party in the White House changes than in years where the incumbent party is reelected.

H2: Competition matters. A transition from a landslide to a more competitive race is likely to affect a bigger shift than one from a competitive election to another. The biggest shift, though would combine both of these hypotheses. A switch from a landslide to another landslide where there is also a change in power translates into the biggest shifts.

Let's look at each of these five electoral transitions:
1984-1988: Big GOP landslide to Moderate GOP landslide
1988-1992: Moderate GOP landslide to Moderate Democratic landslide
1992-1996: Moderate Democratic landslide to Moderate Democratic landslide
1996-2000: Moderate Democratic landslide to Narrow GOP win
2000-2004: Narrow GOP win to Narrow GOP win

There are several types of transitions across these five cycles and that should allow us something better than a passing glance at what we're after and a decent test of our hypotheses. To start, we have a hypothetical threshold in place, 8.3%. From 1984-2004, how many states not only shifted 8.3%, but also changed hands?

Electoral Transitions (1984-2004)*
Year	Toward the Dems	Toward the GOP
1984-1988	AK AZ CA CO CT FL HI ID IL IA KS KY LA ME MA MI MO MT NE NV NH NM NY ND OK OR RI SD TX UT VT WA WV WI WY
Average Shift: 11.76% (toward the Democrats) Total Shifts >8.3%: 35 Number Changing Parties: 9
1988-1992	AL AK AZ AR CA CO CT DE FL GA ID IL IN KY LA ME MD MA MI MS NY NC MO MT NV NH NJ NM NY NC OH PA SC TN TX UT VT VA WA WI WY
Average Shift: 12.92% (toward the Democrats) Total Shifts >8.3%: 39 Number Changing Parties: 22
1992-1996	CT HI ME MA NH NJ NY RI	AK KS
Average Shift: 2.28% (toward the Democrats) Total Shifts >8.3%: 10 Number Changing Parties: 0
1996-2000		AK AZ AR GA ID IN IA KY LA ME MN MS MO MT NE NH ND OH OK SC SD TX UT VT WV WI WY
Average Shift: 10.22% (toward the GOP) Total Shifts >8.3%: 27 Number Changing Parties: 8
2000-2004	VT	AL HI NJ OK RI TN
Average Shift: 2.15% (toward the GOP) Total Shifts >8.3%: 7 Number Changing Parties: 0
* The states in bold and italicized are states that had shifts from one party to the other greater than 8.3% and changed parties from one cycle to the next. Source: Dave Leip's Atlas of US Presidential Elections

There's a lot to look at in this table, so let's try to take it in bits. Let's tackle our hypotheses first. First of all, swings are both bigger and more frequent in years where power changes hands. The only case where there was no change in the incumbent party in the White House and there were shifts was in 1988. George Bush's victory in 1988 had nowhere to go but toward the Democrats following Reagan's thorough trouncing of Mondale in 1984. While there wasn't a change in the party in the White House after the 1988 election, there was a change in who was in the White House. That may explain some of the change. During both Bill Clinton's and George W. Bush's successful reelection bids neither saw many states change more than 8.3% from their initial election, nor did either see a single state change sides.

Not surprisingly, both of those elections (1996 and 2004) saw the smallest average shifts across all 50 states -- less than 2.5% in each. In the three elections that saw a change in power, whether a partisan change or a change in the occupant of the Oval Office, each witnessed average shifts of over 10%. Now, 2008 isn't following a landslide victory, and as a result the incumbent party is much less likely to see such widespread, large shifts and still hold on to power. If, however, Obama wins the 2008 election, we would be likely to see more and bigger shifts, though perhaps not to the degree of the shift in the change election of 1992. We could see a shift similar to 2000, though. The way things look now, the trend could be the exact opposite between 2004-2008 than it was between 1996-2000. Instead of moving from a moderate landslide to a competitive election, the way things appear now, three weeks out, a move from a competitive election to a moderate landslide isn't that far-fetched.

In a change election -- one where there is a change in power -- a shift of 8.3% or more isn't that uncommon from one election to the next.


Recent Posts:
The Electoral College Map (10/14/08)

The Electoral College Map (10/13/08)

A Follow-Up on ACORN