WASHINGTON, D.C. -- The ever-widening gulf between the views of Republicans and Democrats is one of the most significant trends to emerge in U.S. society in the past two decades. This trend is most evident in presidential job approval ratings, but a new Gallup analysis finds that political polarization also exists in Americans' opinions on many other issues.

However, the pattern is not universal. On a few issues, Republicans' and Democrats' views have grown increasingly aligned. And, on other issues, the partisan gap has remained fairly consistent, even as both groups' views have shifted.

Although it is not a comprehensive summary of all attitudes that Gallup has measured over the years, the table that follows summarizes the trends in partisan attitudes on several major policy positions. The baseline year for each trend is Gallup's initial measurement, typically 2000 or 2001, while the most recent results are from either 2016 or 2017.

As Parties Disagree on Policy, Public Opinion Has Grown More Polarized

Many of the increasingly polarized issues are ones on which the leaders in each party have taken strong public positions and that are often included in official party platforms.

Global warming is one such example. Since Gallup began regularly asking public opinion questions about global warming, Democrats have always been substantially more likely than Republicans to be concerned about the phenomenon. But in the mid-2000s, the partisan gap began to grow, largely because of a growing skepticism within the ranks of the GOP. This year, 89% of Democrats said they worry "a great deal" or a "fair amount" about global warming, compared with 40% of Republicans -- a gap of 49 percentage points. This gap was 14 points in 2000.

Gun control is another important example. The difference between the percentage of Republicans who think gun laws should be stricter and the percentage of Democrats who think gun laws should be stricter grew by 28 points between 2001 and 2016. It's worth noting, however, that some aspects of the gun control policy debate are less divisive among the public, such as the requirement that all gun purchasers be subject to background checks.

Shifts in Republicans' and Democrats' views of Cuba reflect specific events. Since Democratic President Barack Obama announced the restoration of diplomatic relations with Cuba in 2014, Democrats have become far more likely than Republicans to have a favorable view of that country.

Other issues with a partisan gap that has grown by 20 or more points include:

The amount of power the federal government has . The partisan gap has grown by 44 points since 2002, with Republicans now much more likely to say they believe the federal government has too much power.

The partisan gap has grown by 44 points since 2002, with Republicans now much more likely to say they believe the federal government has too much power. The level of immigration allowed into the U.S. The gap between Republicans and Democrats has grown by 29 points since 2003, largely due to Democrats' lessened tendency to take the position that immigration should be decreased.

The gap between Republicans and Democrats has grown by 29 points since 2003, largely due to Democrats' lessened tendency to take the position that immigration should be decreased. The government's responsibility for ensuring all Americans have healthcare coverage . Even in 2001, Republicans were much less likely than Democrats to say the federal government should be responsible for ensuring all citizens have healthcare coverage (45% vs. 75%, respectively), but from 2006 to 2009, GOP support for this position fell 20 points to 21% in 2009 -- and it has not recovered considerably since.

Even in 2001, Republicans were much less likely than Democrats to say the federal government should be responsible for ensuring all citizens have healthcare coverage (45% vs. 75%, respectively), but from 2006 to 2009, GOP support for this position fell 20 points to 21% in 2009 -- and it has not recovered considerably since. Whether to prioritize protecting the environment or developing energy sources. The gap between the parties has grown by 23 points from 2001 to 2017, as higher and higher levels of Democrats believe the priority should be given to environmental protection. Republicans' support for protecting the environment over developing energy has not increased as greatly.

The gap between the parties has grown by 23 points from 2001 to 2017, as higher and higher levels of Democrats believe the priority should be given to environmental protection. Republicans' support for protecting the environment over developing energy has not increased as greatly. Sympathies with Israel, Palestine, both or neither in the Middle East situation. Since 2002, sympathy for Israel has grown mightily among Republicans, climbing from 66% to 83% in 2017. Democrats' views on the matter have changed little in the past 15 years.

Since 2002, sympathy for Israel has grown mightily among Republicans, climbing from 66% to 83% in 2017. Democrats' views on the matter have changed little in the past 15 years. Satisfaction with the K-12 public education system in the U.S. As Gallup found in 2016, political polarization regarding the educational system is relatively new -- but certainly real. As noted in the Gallup analysis, this polarization has been driven largely by Republicans, who are notably less happy with the educational system now than they were at the turn of the century. Democrats' level of satisfaction with the system, by contrast, has stayed about the same.

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Gap on Several Social Issues Constant; Healthcare Has Narrowed the Most

On values or moral issues, the trends in polarization are mixed, but the partisan gap on many such issues has mostly stayed the same over the nearly two decades examined here.

Even for issues where the partisan gap has grown -- abortion and the death penalty -- the growth has not been as considerable as it has for issues such as gun control, global warming or immigration, all of which have seen the gap between the parties grow by more than 20 points over time. The partisan gap regarding whether the death penalty should be a punishment for murder grew 18 points between 2000 and 2016; the gap as to whether abortion should be legal under any circumstance has grown 11 points since 2001.

Meanwhile, on several issues, the gap between Republicans and Democrats has barely changed in the last 15 to 20 years, with the size of the gap moving by no more than five points over that time.

These issues include having a baby outside of marriage, same-sex marriage, doctor-assisted suicide and legalization of marijuana, all of which have seen both Republicans and Democrats taking socially liberal positions. Nonetheless, the two partisan groups continue to hold significantly differing opinions on each, even as the gap between their positions has remained relatively constant over time.

Meanwhile, the partisan gap on the perceived quality of healthcare in the U.S. has narrowed significantly, from 21% in 2001 to 0% in 2016. But the narrowing itself results from partisan tendencies. After the passage of the 2010 Affordable Care Act, Republicans became less likely to rate the quality of healthcare in the U.S. positively, while Democrats became more upbeat about the subject.

Bottom Line

The results of this analysis certainly support the conclusion that Americans' party identification has become an increasingly powerful lens through which they view the world around them, as Republicans and Democrats over the years have increasingly diverged in their opinions on a number of important policy and social issues.

The reasons for this increased polarization are complex, but the implications are potentially profound. Elected officials, who themselves increasingly represent more polarized constituents, will find it harder to work in a bipartisan way to address challenges and develop policy solutions when the people of the country hold substantially differing positions based on their party identification.

The inability of members of Congress in recent months to develop a plan to change the Affordable Care Act underscores this phenomenon. In similar fashion, it's not likely to be any easier to achieve consensus on other looming issues such as tax reform and immigration.