There are boxes that US presidential hopefuls have to tick early. They have to start building a campaign team, albeit discreetly. They have to set up a fundraising machine. And they have to visit Iowa, the small but politically crucial state that traditionally kicks off a White House run.

Sarah Palin has ticked the first two and on Friday will tick the third when she is the main speaker at a $100-a-seat Republican dinner in Des Moines, Iowa. The party's sole superstar has not yet said whether she will seek the nomination to take on Barack Obama in 2012. But all the indications point to a run, and Friday's visit is the biggest sign yet.

Democrats may detest her, and so does the Republican establishment, for her perceived lack of sophistication and polarising effect on the electorate. But neither will make the choice in the Iowa caucus. The party activists will, and they are shifting behind her. Long before the contest has formally begun, Palin is fast on the way to becoming unstoppable.

Marilea David, a lifelong Republican, is typical of the fan base, seeing in Palin an alternative to the old-boy network. "I think she is great. She is the only person I am excited about just now," David said over coffee in west Des Moines.

"She is fiscally conservative. She married her husband for love, not money. She does not have perfect kids, which is big for me. She has been totally vetted by the liberal media and they did not come up with anything other than she is a 'hick'."

David, 52, who runs her own home tutoring business, will not be attending Friday's dinner. "I am a broke Republican. But if she runs, I will give her my time. I would love to campaign for her."

The dinner is shaping up as a big media event, with journalists drawn by the will she/won't she drama and by the importance of Iowa, the state where once every four years presidential dreams are either destroyed or begin to be realised.

Kathie Obradovich, political columnist at the Des Moines Register, sees Palin's visit as highly significant. It will be her first since a short stop last year to publicise her autobiography, Going Rogue. "Palin is aware that there are flames of speculation over whether she will run for president and coming to Iowa fans that into a wildfire."

Obradovich believes any clues to whether she is contemplating a run will not come in the speech but in what else she does while in Iowa, whom she speaks to and whether she puts out feelers about potential support.

Although the Iowa caucus to decide whom the state will support as its Republican hopeful is not scheduled until February 2012, candidates often have to begin courting support there at least a year to 18 months in advance, long before they formally declare their candidacy.

Mitt Romney, the multimillionaire and former Massachusetts governor who was John McCain's main rival in 2008, has already recruited a skeleton campaign team in the state. The former House speaker Newt Gingrich visited for a fundraising event last week.

Another potential candidate, Tim Pawlenty, governor of Minnesota, has made five trips to Iowa in the past year. Others weighing whether to run include Haley Barbour, the governor of Mississippi; Mitch Daniels, governor of Indiana; and Senator John Thune, of South Dakota.

A Des Moines Register poll in June gave Romney a 62% favourability rating among Republicans, Palin 58% and Gingrich 56%. Others trailed well behind. Asked why the poll omitted Mike Huckabee, who won in 2008, the Register said that Huckabee had ruled himself out of the race. However, his stance seems to be that he will not make a decision or announcement about 2012 until the 2010 election is over.

Romney, the establishment choice, at present represents the biggest obstacle to Palin. But his name does not generate much warmth or excitement among activists. At 67, Gingrich may be too old.

The dinner will provide firm evidence of Palin's popularity. How many are prepared to stump up the $100? Charlie Gruschow, a Republican and founder of the Des Moines Tea Party, who has taken two tables, seating 20, and filled them, estimated the event could attract 2,500 to 3,000.

Among those planning to attend is Richard Rogers, 60, a pilot who has been active in Republican politics since his teens. From his den in his home in a wealthy Des Moines suburb, he pulled out a glass from the 1964 Barry Goldwater presidential campaign enscribed with the slogan: "The right drink for the conservative taste." He dug out a red sticker he distributed when he was one of the leaders of the Iowa students for Ronald Reagan campaign for the Republican nomination in 1968. He was chairman in Iowa of the Fred Thompson campaign in 2008.

He is not committed to anyone yet, but of the field so far he likes Palin, who reminds him of Reagan, one of the party's best-loved leaders. "We have not seen such enthusiasm and people getting behind a charismatic leader from the conservative-libertarian side since Reagan. She has thought hard about what she believes in, is unapologetic about her beliefs and creates huge enthusiasm ... If she decides to run for president, I will be an enthusiastic supporter," Rogers said.

Momentum has been building this year for a run. In addition to the money pouring in from her autobiography, her speaking engagements and a regular slot on Fox News, Palin has established a political fundraising committee that in the spring alone brought in $865,815. She has been beefing up her staff, including employing speechwriters and hiring consultants to brief her on domestic and foreign policy.

She has been making appearances at high-profile events such as a conservative rally in Washington last month with the popular conservative television commentator Glenn Beck, and again with him in Alaska at a 9/11 rally on Saturday. She has a documentary on Alaska airing nationwide in the autumn and her second book, America by Heart: Reflections on Family, Faith and Flag, is scheduled for publication at the end of the year.

The paperback version of Going Rogue was published in August. The book paints a picture of an outsider who repeatedly takes on the Republican establishment and wins.

Larry Sabato, director of the political centre at the University of Virginia, refuses to predict whether she will stand. "She does not know herself. She is just keeping the doors open. And she wants to keep all of us guessing. Sarah Palin being Sarah Palin will decide at the last minute, when she feels like it. She is not the sort to have a detailed masterplan, following it from day to day."

Sabato predicts that if she runs, she will win Iowa. "More important is what happens if she is nominated. You are looking at a landslide to the Democrats. There is no one the Democrats want more. Obama would expect to win, even if the economy was bad. She is popular among Republicans but in the country as a whole she is unpopular."

The closest she has come to hinting she will run was in an interview with Beck on Fox News in January, telling him she would happily go back to her home in Wasilla, Alaska, to her family and the outdoors, "but if I believe that in some capacity I can help this great nation, I'm going to be willing to sacrifice and to change some things in my lifestyle in order to serve".

She has built up a network of support this year, carefully choosing her endorsements for the November congressional and gubernatorial elections. She has tended to pick insurgent candidates supported by the Tea Party and similar grassroots conservative groups unhappy with the Republican establishment. She has also endorsed what she calls "mama grizzlies", a host of female candidates who believe in strong leadership and family values. Most of her picks, from Rand Paul in Kentucky to Joe Miller in Alaska, have won.

In Iowa itself, she upset Tea Party activists by endorsing the Republican establishment candidate for governor, Terry Branstad, ignoring their candidate, Bob Vander Plaats. As a result Kathy Carley, a Republican and founder of the grassroots group Save Our American Republic, is in unforgiving mood. She is not going to the dinner and will not support Palin. "I used to admire her quite a bit but I have lost faith in her," she said.

Carley, 62, a retired life insurance underwriter, saw the endorsement as a political calculation on the part of Palin, concluding that Branstad was more likely to win than Plaats and that Branstad could help her if she runs in Iowa.

Gruschow was also unhappy with the endorsement. But he is prepared to forgive Palin and, while he hopes some conservative dark horse might yet emerge, he would like to see her stand. "I like to think of Sarah Palin as the Margaret Thatcher of America. I admire her toughness. I would work for her campaign if asked," he said.

• This article was amended on 14 September 2010. The original said that Mike Huckabee had ruled himself out of the 2012 election. This has been corrected.

Sarah Palin's CV

Now 46, she was born in Idaho. Her father, a teacher, liked the outdoors, and moved the family to Alaska.

Education Her higher education was erratic, in part because she had to pay her own way. She had stints as a beauty queen. Jobs afterwards included sports reporting and working in the salmon fishing industry.

Family She has given her five children unusual names, the first one called Track because she and her husband, Todd, liked athletics.

Politics Her first exposure to politics came when she successfully stood for the council in her home town of Wasilla, Alaska, in 1992, before becoming mayor in 2002. Mounting a small-scale campaign that involved driving her children around Alaska, she won the governorship in 2006. She is on the populist right of the Republican party, adored by most Tea Party activists who share her brand of conservatism, summed up by a belief in tight fiscal policies, God, strong defence and family.

Rise to fame She gained national and international recognition in August 2008 when John McCain surprisingly chose her has his running mate in the White House race, a role for which she was unready. Her lack of knowledge of domestic politics and international affairs was cruelly exposed by the media. She resigned as governor of Alaska in 2009 and has since concentrated on writing books, being a Fox News commentator and making profitable speeches. Later this year, she is to star in a documentary called Sarah Palin's Alaska.