A new poll on Wednesday revealed that support for same-sex marriage is growing among Americans.  Forty-two percent favor allowing gays and lesbians to marry legally, up from 37 percent last year, according to the Pew Research Center's latest survey.

Meanwhile, for the first time in 15 years, fewer than half oppose same-sex marriage. Forty-eight percent of Americans are now against same-sex couples marrying, a dip from 54 percent the previous year.

Notably, pluralities of white mainline Protestants and white Catholics now favor allowing same-sex marriage – another first for the Pew Research Center.

According to the poll, white mainline Protestants are more likely to support gay marriage (49 percent) than oppose it (38 percent). In the past two years, 49 percent had expressed opposition. Among those who attend church at least once a week, 35 percent favor gays and lesbians marrying.

A similar shift is seen among Catholics. While opinion was more evenly divided over the past two years, today 49 percent favor gay marriage and 41 percent oppose.

Sixty percent of Americans favor allowing gays and lesbians to serve openly in the military while only 30 percent oppose it. Protestants are also more likely to support gays serving openly in the military (52 percent) than oppose it (37 percent). Evangelicals, meanwhile, are more likely to stand against it (47 percent) than favor it (43 percent).