Half of adult voters (50%) believe the United States should build more nuclear power plants, down eight points from last month and the lowest level of support this year.

Over a third (34%) of voters now disagrees and believes the number of nuclear power plants in this country should not increase, according to the latest Rasmussen Reports national telephone survey.

In April, 58% supported more nuclear plants, and only 25% had the opposite opinion.

The increased political support for expanding the number of nuclear power plants in America marks a significant change after years of resistance driven in large part by the Three Mile Island and Chernobyl accidents in the 1970s. In recent years, support for building more plants has grown due to rising energy prices, increased demand for energy and a desire to lessen U.S. dependence on foreign oil.

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Men and women differ significantly on the question of more nuclear plants. While 66% of men say more plants should be built, only 35% of women agree. The plurality of women (43%) does not think more plants should be built, along with just 24% of men.

Most Republicans (65%) support increasing the number of nuclear power plants in the United States, but only 28% of Democrats agree. Most unaffiliated voters (61%) also support building more plants.

The new survey also finds that 39% of voters believe global warming is caused by human activity, up from 34% in April. However, 44% say long-term planetary trends are most to blame for global warming. Last month, 48% cited this reason.

Despite the rise in voters who say human activity is to blame, the overall results represent a complete reversal from a year ago, when 47% blamed human activity and only 34% blamed planetary trends.

Congress is nearing passage of so-called "cap-and-trade" legislation to combat human pollutants that many say contribute to global warming, but 24% of voters don't even know what the proposed legislation, which is likely to have a significant impact on the economy, is about.

The plurality of voters (44%) sees a conflict between economic growth and environmental protection, up four points from April. Thirty-one percent (31%) do not see this conflict, showing no change over the past four months.

Forty-two percent (42%) of U.S. voters believe that Americans need to make major changes in their lifestyle to save the environment, but 44% disagree.

Most voters (62%) believe finding new sources of energy is more important than reducing the amount of energy Americans consume now. Thirty percent (30%) take the opposite view. Those findings have changed little over the past several months.

Sixty-two percent (62%) see global warming as a serious problem, including 34% who say it is a very serious problem. Those findings are nearly identical to those found in April. Just over a third (34%) of voters does not think global warming is a serious problem, with 16% who say it's not serious at all.

When it comes to President Obama, 49% say he will do a good or excellent job handling energy issues, showing little change this month. Twenty-seven percent (27%) say he will do a poor job handling those issues (see crosstabs).

Most voters (52%) say Obama believes global warming is caused primarily by human activity, up from 49% in April. Only 19% say the president thinks the problem is caused by planetary trends.

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