By Amanda Becker
WASHINGTON, March 19 (Reuters) - Democrats' support is softening for Hillary Clinton, their party's presumed 2016 presidential front-runner, with many favoring an independent review of her personal email use when she was secretary of state.
Support for Clinton's candidacy has dropped about 15 percentage points since mid-February among Democrats, with as few as 45 percent saying they would support her in the last week, according to a Reuters/Ipsos tracking poll. Support from Democrats likely to vote in the party nominating contests has dropped only slightly less, to a low in the mid-50s over the same period.
Even Democrats who said they were not personally swayed one way or another by the email flap said that Clinton could fare worse because of it, if and when she launches her presidential campaign, a separate Reuters/Ipsos poll showed.
The polling showed that nearly half of Democratic respondents - 46 percent - agreed there should be an independent review of all of Clinton's emails to ensure she turned over everything that is work-related.
There was also sizable support among Democrats for the Republican-controlled congressional committee's effort to require Clinton to testify about the emails. Forty-one percent said they backed its efforts to force Clinton's testimony.
"Bottom line is if she didn't do anything wrong, she's fine," said North Carolina resident Renetia Lowery, 48, a Democrat and survey respondent.
The online poll of 2,128 adults from March 10 to March 17 showed that Americans, including two-thirds of Democrats, were aware of the controversy surrounding Clinton's decision to use her personal email rather than a government account, along with a personal server, when she was the top U.S. diplomat from 2009 to 2013.
Clinton has tried to tamp down accusations that she used her personal email account to keep her records from public review, which would support an old political narrative that Clinton and her husband, former President Bill Clinton, are secretive and seek to play by a different set of rules.
(GRAPHIC: Hillary Clinton's emails http://graphics.thomsonreuters.com/15/03/USA-CLINTON-POLL.jpg)
More than a third of Democrats and 44 percent of political independents agreed that the email issue has hurt the former secretary of state politically.
Democratic strategist Ben LaBolt, a former spokesman for President Barack Obama's 2012 campaign, said that the email controversy has been a "galvanizing call for the Clinton campaign-in-waiting to build an organization," by hiring top political communicators who can defend her record. Clinton, who ran for the White House in 2008 and lost to Obama, is expected to announce as early as April that she plans to seek the White House in the November 2016 election.
Former congressional and Justice Department spokesman Brian Fallon, White House aide Jennifer Palmieri, and Jesse Ferguson, who has handled press for Democratic congressional campaigns, are expected to be among the communications experts joining Clinton's campaign. All three are respected in Democratic political circles.
Clinton told a packed room of reporters this month that she used her personal email for official business for the sake of convenience, because it was easier to carry only one device.
"I admire the fact that she has been so strong on a lot of different things, she stands up for what she believes in, but I do think the emails will hurt her, unfortunately," said Patricia Peacock, 49, of Lewiston, Maine, who took part in the survey.
Clinton's office said she has since turned over paper copies of more than 30,000 work emails last year at the State Department's request, but did not hand over about 32,000 that were private or personal records.
Among the emails turned over were 300 related to a 2012 attack on a U.S. consulate in Benghazi that led to the death of a U.S. ambassador and three other Americans, which were subsequently handed over to a Republican-led congressional committee investigating the incident.
The panel has subpoenaed Clinton's remaining emails and said they would like her to testify on the matter before April.
About half of Democrats said they thought Clinton was composed during the March 10 news conference, but 14 percent found her evasive and 17 percent said she avoided answering questions directly.
Survey respondent Tom Trevathan, 74, a retired math professor from Arkansas, said he was "less than happy" with Clinton's performance at the news conference.
"It reminds me of a history she has had not responding thoroughly to inquiries," Trevathan said. "If she would be more open about the situation, and show more leadership in saying what she did and why, I think it would be better."
To explore all the Reuters/Ipsos polling related to Hillary Clinton's emails: http://polling.reuters.com/#!search/clinton%20emails (Additional reporting by Jeff Mason in Washington; editing by Caren Bohan and Howard Goller)