Maine Sen. Susan Collins announced her support for same-sex marriage for the first time Wednesday, hours after the nation’s largest gay-rights group endorsed her for re-election this year over Democrat Shenna Bellows, a longtime advocate of gay couples’ right to marry.

Collins had previously declined to reveal where she stood personally, saying the issue was best handled at the state level.

On Wednesday, however, her campaign issued a statement that many in the gay-rights community had expected much earlier from a lawmaker who is viewed as one of Congress’ friendliest Republicans on lesbian, gay, bisexual and transgender issues.

“A number of states, including my home state of Maine, have now legalized same-sex marriage, and I agree with that decision,” Collins said in the statement. “Today, same-sex couples can be legally married in 19 states and the District of Columbia. Nearly 44% of Americans live in a state where same-sex couples can be legally married, and I believe this number will only continue to grow.”

Earlier Wednesday, Collins was endorsed once again by the Human Rights Campaign, the nation’s largest LGBT advocacy organization.

Collins spokesman Lance Dutson said she made the statement in response to reporters’ renewed questions about her stance, and it was “absolutely not” tied otherwise to the endorsement.

The endorsement itself was not a surprise. The Human Rights Campaign endorsed Collins for election in 2002 and 2008, and gave her an 82 out of 100 in its last congressional voting scorecard – higher than all other Senate Republicans, most of whom scored either zero or 15.

“Senator Susan Collins has played a pivotal role in advancing support for LGBT equality – from her dogged support for the repeal of ‘Don’t Ask, Don’t Tell’ to her critical vote for the Employment Non-Discrimination Act last year,” Chad Griffin, president of the Human Rights Campaign, said in a prepared statement. “HRC is proud to stand with Senator Collins, and with allies on both sides of the aisle like her, because she firmly believes that every American should be evaluated based on their abilities, and not who they love.”

The endorsement was a clear disappointment to Bellows’ campaign and supporters.

As executive director of the American Civil Liberties Union of Maine, Bellows served on the committee that organized statewide campaigns in 2009 and 2012 to legalize same-sex marriage in Maine. Bellows was frequently a spokeswoman during those campaigns.

She also lobbied the Legislature on numerous LGBT issues over the years. And as she points out in campaign speeches and materials, she and her husband delayed their own wedding until same-sex couples could legally marry in Maine, beginning in December 2012.

“I’ve been proud and very privileged to be a leader in the LGBT equality movement for many years,” Bellows said. “As executive director of the ACLU of Maine, I spent every day bringing Republicans and Democrats together to expand civil liberties and strengthen equal protection under the law.”

In an interview, Bellows said she wasn’t surprised by the Human Rights Campaign’s endorsement, calling it an election-year decision.

A poll done in mid-June by the University of New Hampshire Survey Center and commissioned by the Portland Press Herald showed Collins leading Bellows, 72 percent to 17 percent, with 10 percent undecided.

The other three members of Maine’s congressional delegation, Democratic Reps. Mike Michaud and Chellie Pingree and independent Sen. Angus King, have stated their support for same-sex marriage.

Many observers expected Collins to endorse it last year as other members of Congress, including a few Republicans, announced their support amid shifting public attitudes. But Collins steadfastly remained silent on the issue, or said she believed that states should make the call, whether through referendums or legislation.

At the same time, Collins was praised by organizations like the Human Rights Campaign for focusing on other issues of importance to the LGBT community – including several measures tied to same-sex marriage. For instance, she fought to extend federal benefits to the same-sex partners of government employees and twice opposed constitutional amendments to prohibit same-sex marriage.

Collins was a key broker in arranging a Senate vote to end the military’s “Don’t Ask, Don’t Tell” policy, which prohibited openly gay service members.

She also co-sponsored legislation to prohibit prosecutors from discriminating against lesbian, gay, bisexual or transgender jurors in federal trials, and to treat same-sex “permanent partners” the same as heterosexual married couples in immigration cases.

Bellows criticized Collins for not speaking out during the 2009 and 2012 same-sex marriage campaigns in Maine.

“I believe in taking strong stances in favor of constitutional protections and equal rights even when they’re unpopular,” Bellows said. “Remaining silent on some of the biggest civil rights issues of our generation, even after the voters have spoken, isn’t leadership, and it isn’t how Maine became one of the most inclusive states in the country for LGBT rights.”

But Gregory Angelo, executive director of Log Cabin Republicans, an organization that represents gay and lesbian Republicans, said Collins’ support for same-sex marriage is another sign that “the dam has finally broken.”

He said, “As a longtime ally of Log Cabin Republicans who championed repeal of the flawed ‘Don’t Ask, Don’t Tell’ policy and most recently the Employment Non-Discrimination Act, Senator Collins’ declaration of support for civil marriage equality is the latest milestone in a career that has exhibited bold and unwavering support for the LGBT community.”