NEW YORK – It was a day for hat tossing as Senator Clinton, Democrat of New York, entered the race for the Democratic nomination for President and hours later was followed by Senator Brownback, Republican of Kansas, who announced he will seek the Republican nomination.

Governor Richardson, Democrat of New Mexico, is expected to announce his bid to become the nation’s first Hispanic president

Senator Clinton’s bid, while long expected, is historic. She is the first former First Lady – her husband having served from 1993 until 2001 – seeking to become the nation’s first female President.

“I’m in and I’m in to win,” she said in a statement posted on her website Saturday morning. Addressing voters, she said: “I’m not just starting a campaign, though, I’m beginning a conversation with America. Let’s talk. Let’s chat. The conversation in Washington has been a little one-s9ded lately, don’t you think?”

Her announcement follows by less than a week the decision by Senator Obama, Democrat of Illinois, to enter the race. Despite his relative inexperience on the national stage, he has already secured the backing of several prominent former members of the Clinton Administration as well as prominent fundraisers such as billionaire George Soros.

Still, Mrs. Clinton is not expected to have difficult raising money. With a $14 million campaign treasury, Mrs. Clinton starts with a fundraising advantage over the rest of the Democratic field

“I am one of the millions of women who have waited all their lives to see the first woman sworn in as president of the United States — and now we have our best opportunity to see that dream fulfilled,” the Ellen Malcolm, president of EMILY’s list, was quoted by the Associated Press as saying. Emily’s List raises money for Democratic women who run for office

With her star power, network of supporters and donors, and team of political advisers, the 59-year-old Mrs. Clinton long has topped every national poll of potential Democratic contenders. But her tenure as first lady left her a polarizing figure among voters, according to recent polls, leading many Democrats to doubt Clinton’s viability in a general election.

In a statement posted on her Web site, Mrs. Clinton sought to acknowledge and bat away such doubts.

“I have never been afraid to stand up for what I believe in or to face down the Republican machine,” she wrote. “After nearly $70 million spent against my campaigns in New York and two landslide wins, I can say I know how Washington Republicans think, how they operate and how to beat them.”

Recently, Clinton has clashed with many in her own party over the Iraq war.

Clinton supported the 2002 resolution authorizing military intervention in Iraq. She has refused to recant her vote or call for a deadline for the removal of troops. She has announced her opposition to President Bush’s troop increase in Iraq and has introduced legislation capping troop levels.

“A woman candidate could find it easier to run in peacetime, rather than wartime, but Senator Clinton’s tried to position herself as a serious person on national security,” Andrew Polsky, a presidential historian at Hunter College told the Associated Press “But that means she’s staked out difficult position on the war that won’t make it easy for her to get Democratic nomination.”

Her creation of a presidential exploratory committee, announced Saturday, allows her to raise money for the campaign; she already has lined up campaign staff.

In tone and substance, Mrs. Clintons’ videotaped announcement, inviting voters into a national conversation, recalled her first Senate race in New York in 2000, when she conducted a “listening tour” of the state’s 62 counties before formally entering the contest.

She promised a three-day series of Web chats with voters beginning Monday and prepared a campaign swing late this coming week through the early voting state of Iowa, while a visit to New Hampshire was in the works.

On Sunday, Governor Richardson was also set to enter the Democratic field; if elected, he would be the first Hispanic president.

For the short term at least, the outsized candidacies of Mrs. Clinton and Mr. Obama were expected to soak up if not the lion’s share of at least nearly all of attention.

Mr. Obama, who launched his own presidential committee on Tuesday, praised Mrs. Clinton as a friend and colleague.

“I welcome her and all the candidates, not as competitors, but as allies in the work of getting our country back on track,” he said in a statement.

Other Democratic contenders include former Governor Vilsack; Senator Dodd; Representative Dennis Kucinich and Senator Edwards, who represented South Carolina in the upper house and then served as the party’s 2004 vice-presidential nominee. Senator Biden has said he will run and planned to formalize his intentions soon. Senator Kerry, the party’s 2004 standard bearer, is also contemplating another run.

Mrs. Clinton, an influential player in her husband’s political career in Arkansas, emerged on the national scene during the 1992 presidential campaign when husband and wife fought to survive the scandal over Gennifer Flowers’ allegations of a lengthy affair with Mr. Clinton when he was the state’s governor.

The Clintons appeared together on CBS’ “60 Minutes” to talk about their marriage – an appearance that became famous as Mrs. Clinton’s “Stand by Your Man” moment.

As first lady, Mrs. Clinton headed up a disastrous first-term effort to overhaul the health care insurance system. There was more controversy as the couple battled allegations of impropriety over land deals and fundraising, missing records from her former Arkansas law firm, and even her quick profits from an investment in cattle futures.

There was no letup in the second term. The president found himself denying — then admitting — having a sexual relationship with White House intern Monica Lewinsky. As he battled impeachment and possible removal from office, his wife’s poll numbers rose.

Her own political career began to take shape in late 1998 when New York Democrat Daniel Patrick Moynihan announced he would not seek re-election to the Senate seat he had held since 1976.

The campaign trail was not always friendly. For almost every cheer, there was a shouted “Go home, Hillary!” and the emerging Republican theme that carpetbagger Clinton simply wanted to use New York as a launching pad for a later presidential run. But Mrs. Clinton’s first term in the Senate was widely admired not only in New York but among her colleagues in the upper chamber, and she easily won re-election two and a half months ago.

Mr. Brownback jumped into the 2008 presidential race Saturday, a favorite of the religious right now who is now in an uphill battle against better known rivals for the GOP nomination.

“I am a conservative, and I’m proud of being a conservative,” the Kansan was quoted by the Associated Press as proclaiming.

“My family and I are taking the first steps on the yellow brick road to the White House. It’s a great journey,” the two-term senator told hundreds of supporters. He pledged to fight on behalf of the nation’s cultural values and to focus on rebuilding families.

The 50-year-old Mr. Brownback offers himself as a “full-scale Ronald Reagan conservative.”

After Saturday’s speech, he told reporters: “My positions are at the heart of where the Republican Party is. I’m willing to take those positions with all comers.”

Mr. Brownback’s announcement, planned weeks ago, came hours after Mrs. Clinton entered her party’s 2008 race with a posting on Web site with little prior notice.

“I don’t know why she did that. I guess she’s scared of me,” Mr. Brownback said.

The Democratic National Committee issued a statement calling Mr. Brownback “a stubborn ideologue who places his own political agenda over the needs of the American people.”

While Mr. Brownback touched on a wide variety of issues, he laced his speech with the themes that have made him a leader of GOP conservatives and a strong spokesman in Congress for socially conservative Christians.

“He has a consistency that others don’t seem to have,” Hollie Cook, a 30-year-old mother of three from Walkerton, Ind., a Brownback supporter who was traveling with her family to Texas and decided to stop for Saturday’s event told the Associated Press.

A foe of abortion, Mr. Brownback planned to return to Washington to participate in an anti-abortion rally Monday marking the 34th anniversary of the Supreme Court decision that established a nationwide right to the procedure. Mr. Brownback also opposes embryonic stem-cell research and gay marriage.

In his announcement, Mr. 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 believe in “a culture of life.”

“Let’s start following our hearts and work to protect all innocent human life at all stages,” he was quoted as saying by the Associated Press.

He pledged never to sign a tax increase if elected president and proposed scrapping the current income tax law, saying it “should be taken behind the barn and killed with a dull ax.”

Mr. Brownback faces as many as 10 potential GOP hopefuls, including Senator McCain, Governor Romney, and Mayor Giuliani — all with the fundraising skills and experienced campaign staff for the long haul.

Mr. Giuliani is a longtime supporter of abortion rights, gay rights, and gun control.

In recent weeks, conservatives have expressed reservations about Messrs. McCain and Romney, wondering whether their past statements on rights for homosexuals reflect a more moderate view. Many conservatives remain upset with Mr. McCain for pushing a 2002 campaign finance reform law, which they argue stifled conservative groups’ activities.

Mr. Brownback, however, can be trusted, Brenda Travis, a 57-year-old pastor at a Topeka church told the Associated Press. She said she likes his views on abortion and gay marriage.

While he is on solid footing on social issues, Mr. Brownback has broken with some Republicans on the Iraq war and immigration.

He opposes Mr. Bush’s plan to send more troops to Iraq, saying, “Iraq requires a political rather than a military solution.” Mr. Brownback also favors an eventual path to citizenship for some of the nation’s 11 million illegal immigrants.

He was raised on a farm near Parker, Kan., which has a population of 281 and is 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, Mr. Brownback was elected to the Senate, winning the seat Seantor Dole vacated to run for the presidency. Mr. Brownback, who promised to serve no more than two full terms, has said he will not seek re-election in 2010.

The announcements came as the Washington Post and ABC News released a poll showing Mrs. Clinton with a wide lead in the race for the Democratic nomination.

The poll gave Mrs. Clinton 41% in a field with 12 other Democrats including Mr. Obama in second place with 17%, Mr. Edwards in third with 11% and Vice President Gore at 10% in fourth place.

Mr. Kerry garnered 8%, and no other Democrat received more than 3%.

On the Republican side, Mr. Giuliani maintained his lead over Mr. McCain, 34-27. No other candidate received double digits. Mr. Brownback received 1%.