Alluding to another famous Kansan, Dorothy from "The Wizard of Oz," Brownback declared his intention to seek his party's nomination in 2008, saying "My family and I are taking the first steps on the yellow brick road to the White House.
Speaking to a rally in Topeka, the two-term senator said he will fight to renew the nation's cultural values and pledged to focus on rebuilding families.
"Search the record of history. To walk away from the Almighty is to embrace decline for a nation," Brownback said. "To embrace Him leads to renewal, for individuals and for nations."
Brownback laced his speech with the themes that have made him the leader of the GOP's conservative wing and a strong spokesman in Congress for socially conservative Christians. "I am a conservative and proud of being one," he
A fierce foe of abortion, he planned to return to Washington to participate in an anti-abortion rally Monday marking the 34th anniversary of the Supreme Court's Roe v. Wade decision that established a nationwide right to the procedure. Brownback also opposes embryonic stem-cell research and gay marriage.
In his announcement, Brownback said the country needs to support the traditional definition of marriage as a union of one man and one woman and said most Americans "feel deeply in their hearts" for "a culture of life." He called for judges "who want to be judges, not legislators."
"Life is beautiful. We all know this," he said. "Let's start following our hearts and work to protect all innocent life."
He pledged never to sign a tax increase if elected president and proposed scrapping the current income tax law.
Brownback faces a crowded field of potential GOP hopefuls that includes Arizona Sen. John McCain, former Massachusetts Gov. Mitt Romney and former New York City Mayor Rudy Giuliani - all with the fundraising skills and experienced campaign staff for the long haul.
Brownback, 50, offers himself as a "full-scale Ronald Reagan conservative."
"McCain, I think, would be considered by most the front-runner," Brownback acknowledged in a recent interview. "Where I stand on the issues much more reflects the majority of the Republican Party voters."
In recent weeks, conservatives have expressed reservations about McCain and Romney, wondering whether their past statements on rights for homosexuals reflect a more moderate view. Giuliani has been a longtime supporter of abortion rights, gay rights and gun control.
"Brownback, he's a known commodity," said Carrie Gordon Earll, a senior director at the Colorado Springs, Colo.-based Focus on the Family. "Some of the other people who've thrown their hat in the ring, there's debate. Have they always been pro-life? Nobody questions Sam Brownback."
Brownback's causes have included restoring a "family hour" to television, an amendment to the Constitution banning same-sex marriage and legislation to prohibit human cloning and embryonic stem-cell research.
While he is on solid footing on social issues, Brownback has broken with some Republicans on the Iraq war and immigration.
He opposes President Bush's plan to send more troops to Iraq, saying, "Iraq requires a political rather than a military solution." Brownback also favors an eventual path to citizenship for some of the nation's 11 million illegal immigrants.
Brownback was one of the first Republicans to announce an exploratory committee in early December. His candidacy remains a long shot in what has become a crowded GOP field of almost 10 potential candidates.
Brownback's announcement came hours after Sen. Hillary Rodham Clinton, D-N.Y., entered her party's 2008 race.
While conservatives have a major say in picking the Republican nominee, electability also is a factor. GOP pollster Ed Goeas said that while some conservatives have concerns about McCain, they also want a candidate who can beat the Democrat they dislike most.
"All you have to say to conservatives is, 'Hillary Clinton,' and all of a sudden the headache disappears very quickly," Goeas said.
Brownback was raised on a farm near tiny Parker, Kan. - population 281 today - where his parents still live.
He was elected to the House in 1994, part of the Republican revolution that gave the GOP control of both the House and Senate for the first time in 40 years.
Two years later, Brownback was elected to the Senate, winning the seat Bob Dole vacated to run for the presidency. Brownback, who promised to serve no more than two full terms, has said he will not seek re-election in 2010.
Republican pollster Whit Ayres said Brownback faces two major challenges in his bid.
"The first is raising the money necessary to be competitive," Ayres said. "The second is how to expand his base of support beyond the social conservative wing of the party."