Why do so many Republicans dislike Jeb Bush?

Janet DeHart of Emlenton, Pa., loves the Bush family and the two men from the clan who have served as president. But this year, she has no plans to support Jeb Bush for the office.

"I just feel sometimes that I have more zip at 81 than he does," DeHart said.

"What did Donald say? He's 'low-energy.' It's exactly right," she added, referring to GOP front-runner Donald Trump's criticism of Bush. "It looks like he needs someone to walk up from behind him and give him a little nudge."

Bush would seem to have many of the key ingredients of a successful presidential campaign: money, experience and a formidable political name. But he has struggled for a number of reasons, including the most basic of all for a politician: Many people just don't like him.

Nearly 6 in 10 Americans held an unfavorable view of Bush in the latest Washington Post-ABC News poll. Bush was the only Republican with a negative favorability rating: 44 percent said they have a favorable impression of the former governor while 50 percent rated him negatively — a marked shift from November, when 56 percent of Republicans saw him in a favorable light.

Those numbers put him near the bottom of the GOP pack in net favorability ratings, with only Trump — who nonetheless leads the field — faring worse.

The reasons for such disapproval vary, from problems with the candidate himself to weariness over the Bush dynasty. With just two weeks to go until the Iowa caucuses, Bush has failed to overcome the central weaknesses he faced as a presidential candidate from the beginning.

Jay Stonewall, a 54-year-old water department inspector in Billings, Mont., voted for the candidate's father, George H.W. Bush, and his brother, George W. Bush. This year he favors Sen. Ted Cruz, R-Texas.

"The whole Bush family in my opinion is one the first families of America. There's so much honor and respect for his family, for his dad from World War II on down, and they conduct themselves as men should these days," Stonewall said. "But when I first heard that Jeb Bush was running, I thought, that's too much; that's too many Bushes."

Stonewall, DeHart and others participated in the recent Post-ABC poll and said they do not support Bush for the primary. They agreed to answer follow-up questions to explain why.

"To be perfectly frank, I'm not fond of a family dynasty idea. One was enough. I wasn't a big fan of George W., because I thought he was not conservative enough," said Jeff Lemmond, a businessman in Warren, Mich.

"He's a part of the machine and wants to work inside of the machine instead of dismantling the machine and actually representing a substantial part of the country," he added.

Bush strongly disputes such notions on the campaign trail.

"Look, if being the brother of a president and a son of a president means I'm part of the establishment, so be it. I cannot tell you how proud I am of my dad and my brother," he told a voter who asked him about his campaign at a stop last week in Coralville, Iowa. "But if being part of the establishment means you have to be in Washington, then I'm not. Because I've never lived there, I've never worked there."

And what if voters don't like him? "Hell if I know. I don't really care," he said when Newsmax TV asked him recently.

"I'm focused on these early states where my numbers are much better, and I'm going to earn this nomination in a way that will draw people towards our cause," he said. "And I do sense that people are taking it seriously now. Both in Iowa and New Hampshire, people make decisions really late."

Bush's high single-digit support in New Hampshire outpaces his appeal in Iowa or nationally. But even in the Granite State, a Monmouth University poll this month found more Republican likely voters have negative than positive views of his candidacy.

Voters who show up for Bush's town hall meetings in the early states usually leave impressed, if not completely won over. Campaign aides hope that the more direct contact he makes in the coming weeks, the better he'll fare in the early contests.

In a conference call with top donors last week, senior strategist David Kochel said an influx of staffers from campaign headquarters in Miami is helping to build out ground operations in New Hampshire and Iowa that should help Bush beat expectations, the Washington Post reports, citing two people who listened to the call. Bush is aiming to place second in New Hampshire, behind GOP front-runner Donald Trump, Kochel added.

The campaign released two new television ads in New Hampshire that they hope can change perceptions. The first recounts how the candidate's daughter struggled with drug addiction — a message poised to resonate in a state jarred by a record number of drug-related deaths. A second ad shows Bush explaining why he has called Trump a "jerk."

"This is the Jeb Bush I've been waiting for," Kristen Soltis Anderson, a conservative pollster and columnist, tweeted on Thursday after seeing the ad.

But Ron Bonjean, a Republican consultant not working for any presidential candidate, said Bush may now be fighting against irreversible perceptions.

"At this point, the attitudes towards the candidate and the polls have been pretty consistent," he said. "What will make the difference is if the Bush campaign can motivate their supporters to turn out and vote so that he can stay in the game."

Assessing the political risk or reward of Bush's family ties has been harder to track since most national surveys haven't asked voters about them.

Last May, 74 percent of self-identified Republicans said in a Washington Post/ABC News poll that they thought Jeb Bush would come up with new policies in comparison to George W. Bush — and 65 percent said that was a good thing. Such responses suggested that Republicans didn't widely consider Jeb Bush's candidacy a continuation of his brother's two terms.

In March, 75 percent of Republicans and GOP-leaning independent voters said in a Pew Research poll that it didn't bother them that the Bush family continued to play such a prominent role in the Republican Party.

George W. Bush has also rebounded among Republicans, with nearly 9 in 10 approving of his presidency last year, compared to 6 out of 10 in 2008.

But none of this has helped stem the slide for Jeb Bush, suggesting little loyalty to the Bush family among rank-and-file Republicans.

Ultimately, Republican thirst for someone new may be too much to overcome.

Yoran Dreyer, 55, a software company project manager from Staten Island, N.Y., initially considered supporting Bush but chose Cruz instead.

"I don't have anything against him as a person, or against George W. Bush," he said. "But from my perspective . . . I've had enough, and I think the country has had enough of them."