Among the 413 couples registered as domestic partners in the state are Rep. Tammy Baldwin, D-Madison, and Lauren Azar, a Madison lawyer and commissioner with the Public Service Commission.

Baldwin told me earlier this summer that she and Azar would likely register, and her office confirmed this week that the couple had done so.

They have been partners for 13 years.

Couples could start registering Aug. 3 after lawmakers approved the new statewide registry in the 2009-11 budget that took effect July 1. Gov. Jim Doyle had proposed the registry.

Wisconsin is the first state in the country with a constitutional ban against gay marriage and civil unions that also offers some legal recognition of same-sex couples.

A conservative group, Wisconsin Family Action, has asked the state Supreme Court to find the registry unconstitutional. The group argues that the registry confers a legal status "substantially similar" to marriage, which the constitutional ban on gay marriage prohibits.

Proponents say the registry doesn't violate the Constitution, and Doyle, a Democrat, has hired prominent Madison lawyer Lester Pines to defend the state against the lawsuit. Attorney General J.B. Van Hollen, a Republican, said last week he would not defend the state because he believes the registry violates the ban.