Vilsack said the demands of raising large amounts of campaign donations as he competed against better known Democratic rivals was the major reason he decided to quit the race for the White House.
"Today I am announcing that we are ending this presidential campaign."
Political analysts say the media focus on Clinton and Obama, who lead in public opinion polls, made it increasingly difficult for Vilsack to gain public visibility and raise money, two essentials for a successful presidential run. Just a few days ago at a Democratic candidates forum in Nevada, Vilsack argued that the United States should begin an immediate troop withdrawal from Iraq.
"What have you done today to end this war in Iraq? It needs to be ended now. Not six days from now, not six months from now, not six years from now. It needs to be ended now and it's up to you."
Iraq remains the key issue among Democrats running for the White House and the contenders have staked out a wide variety of positions on the conflict. Among those Democrats who oppose an immediate withdrawal from Iraq is Delaware Senator Joe Biden. Biden believes the U.S. must take more time to stabilize Iraq before U.S. troops can leave.
"But ladies and gentlemen, if that civil war metastasizes into a regional war, we are going to be sending your grandchildren back."
Some Democrats running for president have also made a point of saying they made a mistake when they supported President Bush's request to use force in Iraq back in 2002, in advance of the war launched in 2003. This is Connecticut Senator Chris Dodd.
"It was a mistake, in my view, to vote the way we did five years ago on that (use of force) resolution."
Another candidate who says he made a mistake in supporting the force resolution is former North Carolina Senator John Edwards. Edwards says those who initially supported the Iraq war should now admit they were wrong.
"We need a leader who will be open and honest with you and with the American people, who will tell the truth. Who will tell the truth when they have made a mistake, who will take responsibility when they have made a mistake."
Analysts believe Edwards' pointed remarks are directed at New York Senator Hillary Clinton. Clinton has refused demands from some of her rivals that she admit her 2002 vote in support of the war was a mistake.
"My vote was a sincere vote based on the facts and assurances that I had at the time."
Illinois Senator Barack Obama did not attend the Nevada event. Obama was not in the U.S. Senate for the Iraq debate but opposed the war as a state senator in Illinois. Obama and several other Democratic candidates favor a phased withdrawal of U.S. troops from Iraq.
The Obama and Clinton campaigns have exchanged angry statements in recent days over comments made by former Clinton supporter David Geffen. Geffen is a prominent Hollywood film and music producer and criticized Hillary Clinton in the New York Times and said he was supporting Obama for president.
One of the other candidates in the Democratic race, New Mexico Governor Bill Richardson, is urging his fellow Democrats to run positive campaigns, both against each other and against the record of the Bush administration.
"We just cannot criticize the president. There is plenty to criticize. But we should advance our own policies, our own solutions. What is our plan on Iraq? What is our plan on education?"
The early campaign activity has taken some analysts by surprise. But Tom DeFrank of the New York Daily News told VOA's Issues in the News program that optimism among Democrats about their chances next year is driving the early fundraising activity and debate.
"The Democrats smell that is going to be their year in 2008. They think the odds are strong that the next president will be a Democrat, so that ups the stakes on the Democratic side."
Iowa and New Hampshire will kick off the presidential selection process next January. Political analyst Charlie Cook says it is vital for serious presidential contenders to get off to a strong start early next year. Cook spoke on the C-SPAN public affairs TV network.
"Iowa and New Hampshire are hugely, hugely important. And if you do not come in first or second in Iowa, the odds are you are not going to come in first or second in New Hampshire. And if you have not come in first or second in one of those two, I think your chances of winning either party's presidential nomination are under five percent."
On the Democratic side, polls indicate the top contenders at the moment are Senators Clinton and Obama and former Senator Edwards. In the Republican race, surveys show the top three candidates are former New York City Mayor Rudy Giuliani, Arizona Senator John McCain and former Massachusetts Governor Mitt Romney.