Americans are becoming much more liberal on key moral issues they used to frown upon, with support for gay sex, divorce, doctor-assisted suicide and even polygamy on the rise, according to a new Gallup survey.

"This liberalization of attitudes toward moral issues is part of a complex set of factors affecting the social and cultural fabric of the U.S. Regardless of the factors causing the shifts, the trend toward a more liberal view on moral behaviors will certainly have implications for such fundamental social institutions as marriage, the environment in which children are raised and the economy," said the new analysis.

Gallup compared answers on more than a dozen issues from 2001 to today and uncovered the shift, which could impact the upcoming presidential election. They also tested what people felt was morally OK and wrong. The most wrong: extramarital sex.

The issue that shifted most from 2001 to 2015 was "gay relations." Gallup said that in 2001, just 40 percent found it "morally acceptable." That has jumped to 63 percent, and is in-line with some polling on the acceptability of same sex marriage.

Gallup's Social Issues poll finds wide acceptability of gay relations. Gallup image

Other increases in acceptability found in Gallup's May 6-10 Values and Beliefs survey:

-- Having a baby outside marriage, up 16 points to 61 percent.

-- Premarital sex, up 15 points to 68 percent.

-- Divorce, up 12 points to 71 percent.

-- Medical research using stems cells obtained from human embryos, up 12 points to 64 percent.

-- Polygamy, up nine points to 16 percent.

Chart shows the shift in acceptability from 2001 to 2015.

"The biggest leftward shift over the past 14 years has been in attitudes toward gay and lesbian relations, from only a minority of Americans finding it morally acceptable to a clear majority finding it acceptable," said Gallup.

"The moral acceptability of issues related to sexual relations has also increased, including having a baby outside of wedlock -- something that in previous eras was a social taboo. Americans are more likely to find divorce morally acceptable, and have also loosened up on their views of polygamy, although this latter behavior is still seen as acceptable by only a small minority," added the polling company.

Paul Bedard, the Washington Examiner's "Washington Secrets" columnist, can be contacted at pbedard@washingtonexaminer.com.