Barack Obama will spend 2016 trying to define his legacy. Gallup’s analysis of party affiliation cements his long-term legacy on the Democratic Party, at least. In his seven-plus years at the forefront of American politics, Obama’s legacy is one of record Republican affiliation at the state level:

Gallup’s analysis of political party affiliation at the state level in 2015 finds that 20 states are solidly Republican or leaning Republican, compared with 14 solidly Democratic or leaning Democratic states. The remaining 16 are competitive. This is the first time in Gallup’s eight years of tracking partisanship by state that there have been more Republican than Democratic states. It also marks a dramatic shift from 2008, when Democratic strength nationally was its greatest in recent decades.

Gallup charts the decline, which has been dramatic. Eight years ago, when Barack Obama stormed into the forefront of American politics, he had a wide base from which to do so. Twenty-nine states were “Solid Democratic” in Gallup polling that year, compared to only four “Solid Republican” states; with leaners, 35/5. Four years later, the balance was 13/9 and 19/12 with leaners. By the end of 2015, Democrats trailed 11/12, and with leaners 14/20. That’s a flip of 36 states in the gap, or more than two-thirds of the country.

However, that’s only on a state-by-state basis. In terms of popular affiliation, Democrats still hold the lead. Note, though, that the political power of that lead is concentrated in just a few states:

Importantly, even though Republicans claim a greater number of states, Democrats continue to hold an edge nationally in partisanship. In 2015 Gallup Daily tracking data, 43% of all U.S. adults identified as Democrats or leaned Democratic, compared with 40% identifying as Republican or leaning Republican. That is largely because many of the most populous states, including California, New York and Illinois, are Democratically aligned.

We’ve seen this play out in practical terms, too. Republicans control more state legislatures than any time since Herbert Hoover. Thanks to that control, their majority in the House of Representatives will remain solid for years, if not decades, although the Senate is another matter. That means they can produce more effective candidates for other offices, too; Republicans control a record number of gubernatorial seats, too.

The problem for Republicans has been translating that dominance into wins at the presidential level. The chart from Gallup shows one reason the GOP missed a chance in 2012, when Republicans still trailed a bit in this measure, but 2016 gives them a real opportunity to leverage their overwhelming strength in November. That is exactly what my new book GOING RED discusses in depth — how the GOP missed its chance in swing states and counties where Republicans tend to dominate at the local and state level, and how to campaign effectively in a changing environment. The book website will go live in a couple of days, but readers can pre-order it from the Penguin Randomhouse website in the meantime.