Hillary Clinton's negatives keep climbing, raising new questions about her electability and improving the prospects of her chief rivals for the 2008 Democratic presidential nomination.

The New York senator's favorability ratings took a nosedive in mid-April, dropping from 58 percent in February to 45 percent, according to latest Gallup Poll. It was her lowest favorability score since 1993.

A 52 percent majority of the voters now say they have a negative view of her candidacy. That compares to her closest rival, Sen. Barack Obama, who was rated favorably by 52 to 27 percent.

Clinton still held on to her front-runner status in most polls last week, but pollsters and political analysts tell me she is losing the support of strategic blocs in her party's base, including women, liberals and independents, who feel she has waffled on withdrawing U.S. troops from Iraq.

"The recent decline in her image appears to be broad based" among most key voter subgroups, Gallup said.

Even more troubling for her campaign, the Gallup poll of registered voters (taken April 13 to April 15) also showed Clinton losing her double-digit lead over Obama, who now trails her by a slim 5 percentage points in the survey (31 percent to 26 percent). In other polls, the two are virtually tied.

Veteran campaign pollsters, and many Democratic strategists, shocked by her weak numbers, no longer consider her the unbeatable front-runner.

"It's still early in the campaign and it's hard to bet against a Clinton, they're winners. However, the inevitability factor (in her candidacy) is no longer there," independent pollster John Zogby told me.

Zogby has seen similar clues in his own polling data in the first caucus and primary contests that will be held in January. What the latest numbers mean is that, in key states, "where the campaigns have begun in earnest, you have very competitive races and serious questions about Hillary's electability coming from Democrats."

A recent Zogby poll in South Carolina, the first Southern primary contest next year, showed her leading Obama 32 percent to 22 percent. "That's not particularly good," for someone with Clinton's broad name recognition, he said.

The Clinton campaign is privately concerned about her favorability poll scores, but publicly dismisses the Gallup numbers, playing up other polls that have shown her with much stronger leads. But Clinton spokesman Blake Zeff told me, "We are taking nothing for granted and will work hard for every vote."

Even so, her anemic head-to-head numbers in the latest Gallup survey, together with her rising negatives, dominated the backroom buzz in Democratic circles last week.

"Hillary isn't wearing well. It seems as if the more people see her, the less they like her," former Bill Clinton campaign adviser Dick Morris wrote at the Townhall Web site.

"Now for the first time, her low likeability levels are costing her votes, as Democratic-party voters are abandoning her to support Barack Obama," Morris said. "She is losing her base."

National polls are suspect at this stage of the election cycle, which is really all about the candidates' respective strength in the key primaries and caucus states, especially among key demographic subgroups that make up the base of their support.

In Clinton's case, however, Gallup found she had lost 7 percent of her favorability among women in general, 10 percent among younger women aged 18 to 49 and 11 percent among unmarried women.

Zogby underscores the central thrust of Gallup's findings. Democrats appeared to be moving away from Clinton and toward her two chief rivals, Obama and former North Carolina senator John Edwards, he said.

Notably, Edwards, who has 16 percent support in the national Gallup poll, was still running in first place in the latest Iowa caucus polls with 30.3 percent, followed by Clinton with 26.8 percent and Obama with 19.5 percent.

Zogby's other state-by-state polls further confirm that Clinton's numbers are nothing to write home about.

"When you look at Hillary's numbers in the state polls, and the fact that she has 100 percent name recognition among voters, the fact that she's polling in the 20s and low 30s is not good," he said.

Clinton's organization has the best political strategists money can buy, led by the craftiest Democratic campaign Zen master on the planet, her husband Bill Clinton, who plays a central role in every decision she makes. But it's not too premature to say at this point that Clinton's campaign is in trouble.