The ideological consolidation nationwide has happened on both the left and the right of the political spectrum, but the long-term shift among Democrats stands out as particularly noteworthy. The share of Democrats who are liberal on all or most value dimensions has nearly doubled from just 30% in 1994 to 56% today. The share who are consistently liberal has quadrupled from just 5% to 23% over the past 20 years.
In absolute terms, the ideological shift among Republicans has been more modest, in 1994, 45% of Republicans were right-of-center, with 13% consistently conservative. Those figures are up to 53% and 20% today.
But there are two key considerations to keep in mind before concluding that the liberals are driving ideological polarization. First, 1994 was a relative high point in conservative political thinking among Republicans. In fact, between 1994 and 2004 the average Republican moved substantially toward the center ideologically, as concern about the deficit, government waste and abuses of social safety net that characterized the “Contract with America” era faded in the first term of the Bush administration.
But since 2004, Republicans have veered sharply back to the right on all of these dimensions, and the GOP ideological shift over the past decade has matched, if not exceeded, the rate at which Democrats have become more liberal.
A second consideration is that the nation as a whole has moved slightly to the left over the past 20 years, mostly because of a broad societal shift toward acceptance of homosexuality and more positive views of immigrants. Twenty years ago, these two issues created significant cleavages within the Democratic Party, as many otherwise liberal Democrats expressed more conservative values in these realms. But today, as divisions over these issues have diminished on the left, they have emerged on the right, with a subset of otherwise conservative Republicans expressing more liberal values on these social issues.
However, on economic issues and the role of government, Republicans and Democrats are both substantially more consolidated than in the past: 37% of Republicans are consistently conservative and 36% of Democrats are consistently liberal on a five-item subset of the scale restricted to just the items about economic policy and the size of government. In 1994, those proportions were 23% and 21%, respectively.