A Republican Member of the Missouri House of Representatives has been defeated in a GOP Primary, after an aggressive anti-LGBT campaign against her.

State congresswoman Anne Zerr has sat in the House since 2008, and was making a bid for State Senate.

She attracted the ire of evangelicals and anti-LGBT groups in April this year, when she broke a deadlocked committee vote by deciding to vote with the Democrats against SJR 39, a proposed constitutional amendment that would have actively permitted discrimination on the grounds of sexuality.

After the vote, the National Organization for Marriage vowed to “end her political career”, heavily pumping resources into supporting a primary challenge from conservative Bill Eigel. The group started the National Organization for Marriage in Missouri PAC aimed at unseating Zerr.

With 27,643 votes cast, Eigel was victorious in this week’s primary – edging out Zerr by just 385 votes.

NOM president Brian Brown gloated: “Anne Zerr betrayed her constituents and the people of Missouri when she sided with LGBT extremists to defeat SJR 39, which would have given voters the right to protect supporters of marriage from discrimination by governmental entities.

“We did what we promised and went after her, and I couldn’t be happier that she has been defeated.

“Zerr joins a long list of Republicans who have ended their political careers by voting against the interests of people who support marriage as the union of one man and one woman.”

The group pledged to round on other Republican lawmakers who also broke ranks to oppose the legislation, saying: “Whether it takes a few months or several years, we will not rest until all three Missouri Republicans who betrayed supporters of marriage are out of office.

“Zerr was first, Hansen and Rowan are next.”

It is unclear how much influence the group actually has, as Zerr was already under fire over a labour law dispute.

But Zerr maintained she had been targeted by outside “special interests”, saying in a Facebook post: “Ads were mean, hateful, and lies. I have never been treated with such disrespect, and that means the St. Charles County community that has supported me for almost 40 years was treated with disrespect too. I’m pretty protective of my county.

“I leave this job knowing that I voted and acted with integrity and with dignity, always voting the way I did because it was the right thing to do, not because it was the popular thing to do. I leave with no regrets.”

NOM remains active despite financial woes, missing major fundraising targets and facing federal tax complaints.

Last year, NOM was compelled to reveal donor information that revealed links to shadowy groups tied to the Catholic Church.

Despite claiming to be a group that is simply opposed to equal marriage, President Brian Brown revealed his true beliefs in an email after Supreme Court Justice Antonin Scalia passed away.

In the email obtained by PinkNews, Brown referred not just to rulings on same-sex marriage, but cases relating to sodomy laws across the US – expressing clear support for the now-defunct laws criminalising gay sex.