Coloradans will soon be voting in the 2020 presidential election, choosing mainly between incumbent Republican President Donald Trump and Democratic challenger former Vice President Joe Biden. This is a good time to look at how Colorado compares in its voting behavior with the other 49 states.

Throughout the past decade of statewide elections (2010 to 2018), Colorado averaged 52.2% Democratic. Compared to 50 states of the United States, Colorado ranked as the 19th most Democratic state in the 2010s decade. Eighteen states were more Democratic. Thirty-one states were more Republican.

The shift from the decade of the 1980s was quite dramatic. In the 1980s Colorado was the 31st most Democratic state. It has now moved up twelve places to 19th most Democratic state.

Ranking 19th most Democratic places Colorado near the middle of the 50 states but favoring the Democratic Party. There is notable variety in how the 50 states vote in political party terms. The most Democratic state, Hawaii, is 68 percent Democratic. The most Republican state, Wyoming, votes 73.5 percent Republican. The other 48 states fall in a wide range between.

The elections we used to calculate these figures were U.S. president, state governor, and U.S. Senate races.

Close by Colorado’s 52.2% Democratic rank in these state political party rankings are Florida (50.1% Dem), Wisconsin (50.2% Dem), Pennsylvania (52.3% Dem), and Michigan (52.4% Dem). Although most opinion polls show Republican Trump again losing in Colorado in 2020, all four of the other states — Florida, Wisconsin, Pennsylvania, and Michigan — voted for Donald Trump in 2016 and were key components in his surprise electoral victory to the White House. And, not surprisingly, these other four states are considered battleground states in this election.

We calculated Colorado’s two-party voting average in the decade of the 1980s for comparison to the present decade of the 2010s. The 1980s were a strong period of Republican dominance in the nation and Colorado. Ronald Reagan won the presidency twice (1980 and 1984) and the elder George Bush won it once (1988). Reagan’s and Bush’s electoral coattails enabled Colorado Republicans to win many elections lower down on the ballot.

Colorado’s two-party average in the 1980s was 52.4% Republican. That can be measured against the present decade of the 2010s of 52.2% Democratic. That is a shift of 4.6% Republican to Democratic over the four decades. That is not an unusually large shift as state shifts in party voting go. The significant point is that, in moving 4.6 points Democratic, Colorado crossed the 50% mark (52.4% Republican to 50% even to 52.2% Democratic). That is the 50% mark where Republicans stopped winning most of the elections in Colorado and the Democrats started winning most of them.

We went looking for other states where the electorate moved 4 points or so Democratic across the 50% mark that determines which political party wins most of the elections. The closest were Virginia, which shifted 5.5 points Republican to Democratic, and New Jersey, which shifted 6.4 points Republican to Democratic.

At the same time, some states were the opposite of Colorado and moved across the 50% mark from Democratic to Republican. Montana went from 50.6% Democratic in the1980s to 52.9% Republican in the 2010s. Louisiana moved from 51.8% Democratic to 56.3% Republican.

Colorado’s similarity in its vote shifting to Virginia and New Jersey, two high population states on the East Coast, bore out one of our major themes about Colorado voting behavior. Instead of resembling most Rocky Mountain states, which are mainly Republican, Colorado tends to vote similarly to East Coast states which have large population corridors (similar to Colorado’s Front Range population corridor) running through them.

Colorado has obviously shifted Democratic, yet it is unclear how much this will continue. The state has moved steadily more Democratic over four decades, from 52.4 Republican in the 1980s to 52.2% Democratic in the 2010s. Characterized by us as purple (a tossup between red Republican and blue Democratic) in recent years, Colorado is now moving into “leans Democratic” territory.

What explains the shift in partisan hue? There is not a single answer. Here are a few plausible contributors. Democrats tend to do well among well-educated voters with college and advanced degrees. Colorado voters are among the most educated in the nation. Democrats also do well among urban populations, and Colorado has become even more urban in recent decades.

The Republican base in Colorado has been more divided on social issues (abortion, same-sex marriage, and legalized recreational drugs). There are fewer comparable issues dividing Democrats. Finally, Democrats have increased their vote margins in the richer states (Connecticut, New York, New Jersey, California, Maryland, etc.) The strong economic growth in Colorado in recent decades has pushed our state into this more prosperous group.