Sarah Palin's baby shower included a surprise guest: her own baby. He had arrived in the world a month early, so on a sunny May day, Palin, the governor of Alaska, rocked her newborn as the women around her -- her closest friends, sisters, even her obstetrician -- presented her with a potluck meal, presents and blue-and-white cake.

Most of the guests, along with the rest of Alaska, had learned that Palin was pregnant only a few weeks before. Struggling to accept that her child would be born with Down syndrome and fearful of public criticism of a governor's pregnancy, Palin had concealed the news that she was expecting even from her parents and children until her third trimester.

But as the governor introduced her son that day, according to a friend, Kristan Cole, she said she had come to regard him as a blessing from God. "Who of us in this room has the perfect child?" Palin asked.

Since that day, Trig Paxson Van Palin, still only 143 days old, has had an unexpected effect on his mother's political fortunes. Before her son was born, Palin went to extraordinary lengths to ensure that his arrival would not compromise her work. She hid the pregnancy. She traveled to Texas a month before her due date to give an important speech, delivering it even though she suspected her amniotic fluid was leaking. Three days after giving birth, she returned to work.

But with Trig in her arms, Palin has risen higher than ever. Sen. John McCain, the Republican nominee for president, says he selected her as his running mate because of her image as a reformer, but her stirring personal story has proved its appeal. In just a few months, she has gone from hiding her pregnancy from those closest to her to toting her infant on stage at the Republican National Convention.

No one has ever tried to combine politics and motherhood in quite the way that Palin is doing, and it is no simple task. In the last week, the criticism she feared in Alaska has exploded into a national debate. On blogs and at PTA meetings, voters alternately cheer and fault her balancing act, and although many are thrilled to see a child with special needs in the spotlight, some accuse her of exploiting Trig for political gain.

But her son has given Palin, 44, a powerful message. Other candidates kiss strangers' babies; Palin has one of her own. He is proof of Palin's convictions against abortion and her belief that women can balance family and career. And on Wednesday night in St. Paul, she appointed herself a guardian of disabled children all over the country. "Children with special needs inspire a special love," Palin said, echoing the message she had shared with friends at the shower.

Hiding the pregnancy

By last winter, Palin seemed to have everything she had ever wanted. She had raised four children while turning herself into a rising star of the Republican Party of Alaska and then the national one. But then the still-new governor discovered she was pregnant. Piper, the youngest of the Palin brood, was 6. The family had long since given away their crib and high chair.

A few weeks later, after an amniocentesis -- a prenatal test to identify genetic defects -- Palin learned the results. ("She likes to be prepared," said Heather Bruce, her older sister.) With her husband, Todd, away at his job in the oil fields of the North Slope, Palin told no one for three days, she later said.

Once they reunited, the Palins, evangelical Christians, struggled to understand what they would face. Children with Down syndrome experience varying degrees of cognitive disability and a higher-than-average risk of hearing loss, hypothyroidism and seizure disorders. About half are born with heart defects, which often require surgery.

The couple decided to keep quiet about the pregnancy so they could absorb the news, they told people later.

And there were political factors to consider. "I didn't want Alaskans to fear I would not be able to fulfill my duties," Palin told People magazine last week.

The governor began an elaborate game of fashion-assisted camouflage. When Vogue photographed her, five months pregnant, for a profile in January, she hid in an enormous green parka. At work, she wore long, loose blazers and artfully draped accessories.

As Palin's clothes grew tighter, Alaskans began to talk. She told several aides that she was pregnant, and a week or so later, she told her parents and her children, who called other relatives.

On March 5, as she was leaving her office for a reception, she shared the news with three reporters. "We're expanding," the governor said brightly, according to an aide, Sharon Leighow.

"You're expanding state government?" one of the reporters asked. "No, my family's expanding," she said. "I'm pregnant."

She assured them she would not take much time off: She had given birth to Piper on a Monday and returned to work on a Tuesday, the child in tow. "To any critics who say a woman can't think and work and carry a baby at the same time," she said, "I'd just like to escort that Neanderthal back to the cave."

There was no mention of the baby's condition. In private, the Palins slowly started to share their unborn son's diagnosis. They wrote a long letter to Bruce, Palin's sister, who has an autistic son, explaining how they had come to embrace the challenges their baby would bring.

From Texas to Alaska before delivery

In mid-April, Palin and her husband flew to Texas for an energy conference with fellow Republican governors. Around 4 a.m. on the day of her presentation, Palin stirred in her hotel room to an unusual sensation. She guessed she was leaking amniotic fluid, she told the Anchorage Daily News. She woke her husband and called her doctor back home. Go ahead and give the speech, said the doctor, Cathy Baldwin-Johnson, who declined to comment for this article.

So Palin marched through the day. In her lunchtime speech, Palin held forth on the trillions of cubic feet of gas in the Alaskan Arctic, competitive bidding over pipeline construction and natural gas combustion. As she left the podium, Gov. Rick Perry of Texas joked, "You're not going to give birth, are you?"

Palin just laughed.

"Nobody knew a thing," said Linda Lingle, the governor of Hawaii. "I only found out from my security detail on the way home that she had gone into labor and that she had gone home to Alaska."

In fact, Palin was not yet in labor, and her doctor thought she had time. So the governor flew to Seattle, continued on to Anchorage and then drove to a small hospital near her hometown, Wasilla -- a journey of at least 10 hours.

"She wanted to get back to Alaska to have that baby," said a friend, Curtis Menard. "Man, that is one tough lady."

When Palin arrived at the hospital, she was still not in labor, so her doctor induced it, her sister Bruce said. Trig was born early the next morning, weighing 6 pounds, 2 ounces.

Parents who were in the next delivery room said the scene in the maternity ward looked like any other, with no security detail in sight. The three Palin daughters came and went, and as Todd Palin passed through the corridors, he stopped to accept congratulations.

Inside Palin's room, her daughter Willow, 14, immediately noticed her new brother's condition, according to People magazine. "He looks like he has Down syndrome," Willow said. "Why didn't you tell us?"

Palin had wanted to let the news of the pregnancy sink in first, said Cole, her friend. She had intended to tell her family more after she returned from Texas. Then the baby arrived.

Her hesitation gone, Palin glowed with maternal pride. "Sarah was absolutely ecstatic," said a friend, Marilyn Lane. After months of reflection and prayer, friends say, the Palins had come to believe God had chosen to send them Trig. Later that day, Palin sent an e-mail message to her relatives and close friends about her new son, Bruce said. She signed it, "Trig's Creator, Your Heavenly Father."

"Many people will express sympathy, but you don't want or need that, because Trig will be a joy," Palin said. "Children are the most precious and promising ingredient in this mixed-up world you live in down there on Earth. Trig is no different, except he has one extra chromosome," the governor wrote.

A three-day maternity leave

Palin's three-day maternity leave has become legend among mystified mothers. But aides say she eased back into work, first stopping by her office in Anchorage for a meeting, bringing not only the baby but also her husband to look after him.

Many high-powered parents separate work and children; Palin takes a wholly different approach. "She's the mom and the governor, and they're not separate," Cole said. Around the governor's offices, it was not uncommon to get on the elevator and discover Piper, smothering her puppy with kisses.

"She'll be with Piper or Trig, then she's got a press conference or negotiations about the natural gas pipeline or a bill to sign, and it's all business," said Angelina Burney, who works across the hall from Palin's office in Anchorage. "She just says, 'Mommy's got to do this press conference.'"

Accordingly, Palin installed a travel crib in her Anchorage office and a baby swing in her Juneau one. Todd Palin took a leave from his job as an oil field production operator, and campaign aides said he was doing the same now. At home and on the trail, he will take care of his son, who is about to become one of the best-traveled, highest-profile babies in the country.