MADISON, Wis. (AP) — Since U.S. District Judge Barbara Crabb ruled the National Day of Prayer unconstitutional, critics have declared what they think of her: A Marxist. A moron. A disgrace.

One person wrote that he was praying God removes her from office. Several warned she is headed to hell. GOP Rep. Ted Poe of Texas took to the House floor to taunt: ‘‘What’s next, Judge Crabb? You going to ban Thanksgiving and Christmas as national holidays?’’

Crabb, a 31-year veteran of the bench in this liberal state capital, has faced harsh criticism before. Those close to her say she isn’t afraid of it.

In her ruling last month, Crabb said the law creating the tradition being observed Thursday is an unconstitutional call to religious action. She quickly became a magnet in the contentious debate over the role of religion in public life — denounced by Christian activists for overstepping but hailed as courageous by atheists, agnostics and non-Christians who feel excluded from the day.

‘‘BABS, we Americans and veterans will be praying on the public square on May 6,’’ one Vietnam veteran from Cleveland wrote, part of the one-inch thick stack of critical e-mails and letters her office has received. ‘‘Try to stop us.’’

President Obama, whose administration is appealing the ruling, has urged citizens to ‘‘pray, or otherwise give thanks’’ for the nation’s freedom and blessings. And Crabb put enforcement of her ruling on hold pending the appeal, meaning thousands of prayer events will go on as scheduled.

But advocates for the separation of church and state plan to gather Thursday as well, rallying in front of the state Capitol to praise Crabb’s ruling and call for an end to the National Day of Prayer.

The 71-year-old judge, who declined an interview request, has never been afraid to make rulings unpopular with ‘‘Joe Blow on the street’’ when she believes the law calls for it, said Krista Ralston, who was Crabb’s first law clerk after she was promoted to judge three decades ago.

In the late 1980s, protesters burned Crabb’s likeness in effigy after she allowed Indian tribes to spearfish off their reservations — a practice some white fishermen believed ruined their sport. Demonstrators threw rocks, uttered racial slurs and accused Crabb of giving Indians special treatment.

‘‘Talk about developing thick skin — that’ll do it for you,’’ said Kendall Harrison, who worked for Crabb as a law clerk from 1995 to 1997.

Crabb, who graduated from the University of Wisconsin law school in 1962, served in the 1970s as a federal magistrate under the late U.S. District Judge James Doyle, the father of Wisconsin’s Democratic governor. Appointed to the bench in 1979 as Wisconsin’s first female federal judge, Crabb is called thoughtful, fair and hardworking by lawyers who appear in her courtroom.

In 1997, she upheld a Wisconsin law that requires women to wait 24 hours before having an abortion, saying U.S. Supreme Court precedent required her to rule that way. She helped fix inhumane conditions at Wisconsin’s maximum security prison, ordering officials to stop housing mentally ill inmates there and to install air conditioning in hot cells.

Yet she hands criminals the stiff prison terms called for by federal guidelines even when she would like to be more lenient, said her husband of 50 years, Ted Crabb.

Defense lawyer Chris Van Wagner, who recently tried a contested arson case in her courtroom, said his client could not have asked for a fairer trial even though he was convicted and later sentenced to prison. ‘‘You can disagree with her rulings, but you have to give her praise,’’ he said.

In the National Day of Prayer decision, Crabb found Congress violated the First Amendment by passing a law directing the president to encourage citizens to pray, and said the law amounted to a government endorsement of a religious exercise. She emphasized that her conclusion was not a judgment ‘‘on the value of prayer or the millions of Americans who believe in its power.’’

But she said the government can no more encourage citizens to pray than to ‘‘fast during the month of Ramadan, attend a synagogue, purify themselves in a sweat lodge or practice rune magic.’’

‘‘In fact, it is because the nature of prayer is so personal and can have such a powerful effect on a community that the government may not use its authority to try to influence an individual’s decision on whether and when to pray,’’ she wrote.

Annie Laurie Gaylor, co-president of the Freedom From Religion Foundation, which brought the lawsuit against the law, said she was confident Crabb’s decision would be upheld.

‘‘She’s a very venerable, senior federal judge and she did a superb job anticipating the appeal,’’ Gaylor said.

A hallmark of Crabb’s tenure has been the belief that all litigants deserve an opportunity to be heard and should have a prompt resolution. Along with U.S. District Judge John Shabaz, she adopted rules that have made the Western District of Wisconsin one of the speediest federal courts in the nation.

After Shabaz went on medical leave in 2008 and retired last year, Crabb worked long hours as the district’s only judge. Shabaz’s successor was confirmed in March.

Then, once the Senate confirms another judge for the district, Crabb plans to take senior status and work part-time so she has more time for birding and other hobbies, Ted Crabb said. They have two adult children and do not belong to a church, he said.

‘‘She’s a very considerate judge. She’s not a flamboyant judge. She takes her work seriously,’’ her husband said. ‘‘When Judge Shabaz had to take medical leave, she stepped up to the plate and kept the court going. She’s a real servant of the court, and she loves the law.’’