Last week, we released the 25th Anniversary edition of the Cook Partisan Voting Index (Cook PVI℠). The Cook PVI measures how each state and district performs at the presidential level compared to the nation as a whole. Among the many insights gleaned by my colleague David Wasserman from that report was that “Republicans continue to benefit from an electoral map tilted in their favor on nearly all levels.”

In fact, when looking exclusively at the Electoral College map, Republicans are enjoying a stronger advantage than at any point in the 25-year history of the Cook PVI. In 1997, the median Electoral College vote (located in Iowa) had a PVI score of D+1; meaning that the median Electoral College vote was one point more Democratic than the nation as a whole. By 2005, the median Electoral College state (Florida) had a PVI of R+1. In 2021, Wisconsin, with a PVI score of R+2, is the median Electoral College vote. So, if, for example, a Republican presidential candidate were to get 49 percent of the national popular vote, we should expect that Republican to get 51 percent of the vote in Wisconsin. 

Fundamentally, what the Cook PVI scores make apparent is that a Republican presidential candidate can lose popular vote by narrow margin and still win an Electoral College majority. That, however, is almost impossible for a Democrat to replicate. Another way to look at it is that Democrats need to win the popular vote by at least three points (but more realistically 4 points) to feel confident that it will translate to an Electoral College win. 

Let’s break this down a bit. Since 2000, a Republican presidential candidate has never taken more than 51 percent of the national popular vote (George W. Bush in 2004). Bush’s 2004 win was the only time in the last six presidential elections where a Republican candidate took more than 48 percent of the popular vote. Even so, Republicans have been able to win the presidency in three of those six elections.

If these patterns continue to hold, the 2024 GOP nominee taking just 48 percent of the two-party popular vote could still win a comfortable Electoral College majority. Here’s how that could happen.

The 2021 Cook PVI finds six swing states — Arizona, Florida, Georgia, North Carolina, Pennsylvania and Wisconsin — with a PVI score of R+2 or higher.  In those states, which lean 2 points or more Republican than the national popular vote, a GOP nominee could be reasonably expected to win those states (add 2 points to the 48 percent national vote and you have 50 percent). Ultimately, it would produce an Electoral College tally of 291 Republican to 247 Democratic. 

Now, let’s flip the script and say that a Democrat loses the popular vote by 2 points — taking just 48 percent of the two-party vote. The 2021 Cook PVI shows three swing states with a Cook PVI of D+2 or higher; Maine, New Mexico, and Virginia. But, two other states — Minnesota and New Hampshire — have PVI scores of D+1; not enough to expect a victory for the Democrat. This could mean an Electoral College blowout for Democrats — 218 to 320 for the Republican nominee. 

Compare that 320 to 218 shellacking to 2004, when John Kerry lost the popular vote by 3 points. While he lost the Electoral College, it was by a much narrower margin; 251-286. 

Here are some other takeaways from the 25th Anniversary Edition of the Cook PVI. 

Fewer “swing states” Our first Cook PVI, which combined the results of the 1992 and 1996 presidential elections, found 19 ‘swing’ states, states with a PVI between D+3 and R+3. Today, there are just 13. But interestingly enough, about half of those 13 states — Nevada, New Hampshire, Florida, New Mexico, Pennsylvania, and Wisconsin — have been swing states since 1997. Three states — Nevada, New Hampshire, and New Mexico — have become a little more Democratic-leaning, while two others, Pennsylvania and Wisconsin, have become more Republican. Florida wins the award for stability; since 1997 the Sunshine state’s Cook PVI has been between R+1 to R+3. 

More hyper-partisan states: And, as we’ve seen in the House, there are now more “mega-partisan” states than ever. In 1997, only nine states had a PVI of 10 points or more. Today, there are 23 states that are 10 points or more Republican or Democratic than the nation as a whole. 

Warning lights for democrats: Lots of attention has been paid to the Sun Belt states that have steadily moved away from their GOP moorings. As recently as the 2009 PVI ratings, states like North Carolina, Georgia, Arizona, Virginia and Arizona were still in the lean Republican range. Today, all five are in the hyper-competitive category. But, less attention has been paid to some of the states that have long been considered ‘safely” Democratic, that have moved in the GOP direction over the last few presidential elections. Maine, which splits its electoral votes by CD, had a PVI of D+5 back in 1997. It dropped to D+3 in 2017 and now sits at D+2. And, Minnesota, a state that hasn’t supported a Republican nominee for President since 1972, now has a PVI of just D+1. 

Notes about Cook PVI℠ Data & Methodology

In August of 1997, The Cook Political Report introduced the Cook Partisan Voting Index (Cook PVI) as a means of providing a more accurate picture of the competitiveness of each of the 435 congressional districts. Whereas our race ratings reflect our outlook for which party will win the next election in each state and district, the Cook PVI takes a longer view and seeks to measure the underlying partisanship of each district relative to the nation as a whole.

We have released new PVI scores following every election and instance of redistricting since 1996, each time taking into account the prior two presidential elections. Prior to 2020, the Cook Political Report contracted with Clark Bensen's firm Polidata to calculate presidential results by congressional districts and PVI scores. In 2021, the Cook Political Report teamed up with Dave Leip's Atlas of U.S. Presidential Elections to calculate 2020's results by district.

Beginning with this decade, we're making a slight formula change to how we calculate PVI scores: instead of using a 50/50 mix of the two most recent presidential elections to assess partisanship as we've done in the past, we're switching to a 75/25 weighting in favor of the more recent presidential election. For the 2022 dataset, that means that the 2020 result in each state district is weighted three times as heavily as the 2016 result.
Since we first launched the Cook PVI in 1997, there's been a dramatic increase in "straight-ticket" voting, with fewer voters choosing candidates of different parties for the White House and Congress. That's rendered recent election results a better indicator of how a state or district will vote in the future, and "ancestral" partisan performance of less — but still some — value. In short, as electoral realities have changed, so too must the Cook PVI.


Research Associate Matthew Klein contributed to this report.

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