Emily Nordling has never met a Muslim, at least not to her knowledge. But this spring, Ms. Nordling, a 19-year-old student from Fort Thomas, Ky., gave herself a new middle name on Facebook.com, mimicking her boyfriend and shocking her father.

“Emily Hussein Nordling,” her entry now reads.

With her decision, she joined a growing band of supporters of Senator Barack Obama, the presumptive Democratic presidential nominee, who are expressing solidarity with him by informally adopting his middle name.

The result is a group of unlikely-sounding Husseins: Jewish and Catholic, Hispanic and Asian and Italian-American, from Jaime Hussein Alvarez of Washington, D.C., to Kelly Hussein Crowley of Norman, Okla., to Sarah Beth Hussein Frumkin of Chicago.

Jeff Strabone of Brooklyn now signs credit card receipts with his newly assumed middle name, while Dan O’Maley of Washington, D.C., jiggered his e-mail account so his name would appear as “D. Hussein O’Maley.” Alex Enderle made the switch online along with several other Obama volunteers from Columbus, Ohio, and now friends greet him that way in person, too.

Mr. Obama is a Christian, not a Muslim. Hussein is a family name inherited from a Kenyan father he barely knew, who was born a Muslim and died an atheist. But the name has become a political liability. Some critics on cable television talk shows dwell on it, while others, on blogs or in e-mail messages, use it to falsely assert that Mr. Obama is a Muslim or, more fantastically, a terrorist.

“I am sick of Republicans pronouncing Barack Obama’s name like it was some sort of cuss word,” Mr. Strabone wrote in a manifesto titled “We Are All Hussein” that he posted on his own blog and on dailykos.com.

So like the residents of Billings, Mont., who reacted to a series of anti-Semitic incidents in 1993 with a townwide display of menorahs in their front windows, these supporters are brandishing the name themselves.

“My name is such a vanilla, white-girl American name,” said Ashley Holmes of Indianapolis, who changed her name online “to show how little meaning ‘Hussein’ really has.”

The movement is hardly a mass one, and it has taken place mostly online, the digital equivalent of wearing a button with a clever, attention-getting message. A search revealed hundreds of participants across the country, along with a YouTube video and bumper stickers promoting the idea. Legally changing names is too much hassle, participants say, so they use “Hussein” on Facebook and in blog posts and comments on sites like nytimes.com, dailykos.com and mybarackobama.com, the campaign’s networking site.

New Husseins began to crop up online as far back as last fall. But more joined up in February after a conservative radio host, Bill Cunningham, used Mr. Obama’s middle name three times and disparaged him while introducing Senator John McCain, the presumptive Republican nominee, at a campaign rally. (Mr. McCain repudiated Mr. Cunningham’s comments).

The practice has been proliferating ever since. In interviews, several Obama supporters said they dreamed up the idea on their own, with no input from the campaign and little knowledge that others shared their thought.

Some said they were inspired by movies, including “Spartacus,” the 1960 epic about a Roman slave whose peers protect him by calling out “I am Spartacus!” to Roman soldiers, and “In and Out,” a 1997 comedy about a gay high school teacher whose students protest his firing by proclaiming that they are all gay as well.

“It’s one of those things that just takes off, because everybody got it right away,” said Stephanie Miller, a left-leaning comedian who blurted out the idea one day during a broadcast of her syndicated radio talk show and repeated it on CNN.

Ms. Miller and her fellow new Husseins are embracing the traditionally Muslim name even as the Obama campaign shies away from Muslim associations. Campaign volunteers ushered two women in head scarves out of a camera’s range at a rally this month in Detroit. (The campaign has apologized.) Aides canceled a December appearance on behalf of Mr. Obama by Representative Keith Ellison, a Minnesota Democrat and the first Muslim congressman.

Mr. Obama may be more enthusiastic, judging from his response at a Chicago fund-raiser two weeks ago. When he saw that Richard Fizdale, a longtime contributor, wore “Hussein” on his name tag, Mr. Obama broke into a huge grin, Mr. Fizdale said.

“The theory was, we’re all Hussein,” Mr. Obama said to the crowd later, explaining Mr. Fizdale’s gesture.

Some Obama supporters say they were moved to action because of what their own friends, neighbors and relatives were saying about their candidate. Mark Elrod, a political science professor at Harding University in Searcy, Ark., is organizing students and friends to declare their Husseinhood on Facebook on Aug. 4, Mr. Obama’s birthday.

Ms. Nordling changed her name after volunteering for Mr. Obama before the Kentucky primary.

“People would not listen to what you were saying on the phone or on their doorstep because they thought he was Muslim,” she said.

Ms. Nordling’s uncle liked the idea so much that he joined the same Facebook group that she had. But when her father saw her new online moniker, he was incredulous.

“He actually thought I was going to convert to Islam,” Ms. Nordling said.