Liberal activists plan to begin airing a television ad against Hillary Clinton in Iowa this week, the first non-Republican negative ad aimed at a Democratic presidential candidate.

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The group, Democratic Courage, has accused Clinton of making policy decisions on the basis of polls, not convictions. It planned to introduce the ad Tuesday.

Glenn Hurowitz, the group's president, described the spot as a modest buy that would run on cable only, meaning it won't be seen as much as ads by Clinton and rival Barack Obama, who are spending hundreds of thousands of dollars on ads in the state.

Democratic Courage is a political action committee, financed by contributions of no more than $5,000 per person.

The group's Web site said it is "dedicated to electing a progressive, courageous, and winning Democratic presidential candidate.

"Unfortunately, Hillary Clinton has fallen short on that standard - repeatedly giving in to pressure from Republicans and corporate lobbyists. She has failed to provide the strong leadership voters will demand."

Hurowitz said, "We are concerned that she wouldn't be the best candidate in the general election or the best president because she is so easily bullied by the Republican attack machine."

Republican presidential candidates Mitt Romney, Rudy Giuliani and John McCain have all run ads putting Clinton in a negative light.

Hurowitz said the group does not plan to endorse any candidate, though he said it may run a negative ad against another Democrat in the field. He would not identify who that would be. He said the extent of the group's advertising would depend on the amount of donations its first ad generates.

Clinton is in a virtual three-way tie in Iowa with Obama and John Edwards. The Iowa caucuses are only one month away.

In the meantime, Clinton is turning up the heat on her closest Democratic rival, Barack Obama.

Campaigning in Iowa, with a month to go before the nation's first political caucuses, Clinton suggested the Illinois senator has too little experience for the White House.

An Obama campaign spokesman said the Illinois senator doesn't need lectures in political courage "from someone who followed George Bush to war in Iraq."

Clinton also accused Obama of a "rush to campaign," which caused him to miss a vote on a resolution that named an Iranian group as a terrorist organization.

The heated rhetoric underscores the tightness of the race. Some polls show a dead heat between Clinton and Obama in Iowa, and others give Obama the edge. Former Sen. John Edwards is also in strong contention.

Health Care Helps Clinton

Health care and Iraq dominate Democrats' concerns in the three pivotal early voting states of the 2008 presidential race, according to a new Associated Press poll run in conjunction with the Pew Research Center.

Clinton has clear leads in New Hampshire and South Carolina, and has a slight edge over Obama in Iowa, building on her emphasis on the health-care issue and her broad but more fragile trust among Democrats on Iraq, the survey said.

The Iowa results are somewhat different from a Des Moines Register poll released Sunday, which gave the edge there to Obama.

The three-state AP/Pew poll found Democrats enthusiastic about their overall presidential field. Most rate it strongly, and they spiritedly back the contenders they prefer.

Clinton has amassed strong support among crucial groups including female, older, less-educated and lower-income Democrats -- significant because women and older voters in particular have dominated these primaries and caucuses in the past.

The AP/Pew poll found Clinton is essentially tied with Obama in Iowa, 31 percent to 26 percent, with John Edwards at 19 percent and Bill Richardson at 10 percent.

In New Hampshire Clinton has 38 percent, Obama 19 percent, Edwards 15 percent, Richardson 10 percent.

In South Carolina Clinton has 45 percent, Obama 31 percent, Edwards 10 percent.

The Des Moines Register poll of Democrats said Obama got 28 percent, while Clinton had 25 percent and John Edwards had 23 percent. Other candidates were in single digits. More than half of likely caucus-goers in both races say they could change their minds. A chunk are undecided.