A poll released Monday by Gallup shows a majority of Democrats support gay marriage and that overall opposition to the institution in the United States has decreased slightly.

Gallup's latest Values and Beliefs Poll released Monday found 56% of Democrats now say gay and lesbian couples should be allowed to legally marry, a 23% increase since 1996, the first year the question was asked.

Republican support has also increased to 28 percent, up from 16% 14 years ago.

Overall, opposition to the institution has decreased slightly, from 57% last year to 53%, while support has increased, up 4 percentage points from last year to 44%.

“These political differences in support for gay marriage may stem from even larger differences by religion,” the poll's authors say.

Eighty-one percent of Americans who claim no religious affiliation favor legal gay marriage. That compares to 48% support among Catholics and 33% among Protestants.

While opponents continue to outnumber supporters, in some states the opposite is true. Polls in Massachusetts, California and even New York point to a tipping of the scales.

The poll's results are based on 1,029 telephone interviews with adults conducted during the first week in May.