Polls show a growing number of Americans believe the Democratic front-runner cannot be trusted, however, and questions about the email have dogged
In a sign of Democrats' mounting concern, former New Mexico Gov.
Richardson, who served as secretary of Energy in Bill Clinton's administration, said he might have set up the same system if he had had a Cabinet position in recent years.
"I would have said, 'You know what? I don't want an official classified email system. I want to have my own private server," he said. "Because of WikiLeaks, because of hacking, because of leaks."
He compared it to former Secretary of State
Clinton's campaign announced this month that it was turning over the private server and a thumb drive with backup copies of the work emails to the Justice Department, which is investigating whether a security breach occurred.
Richardson said he stands by his decision to endorse then-Sen.
Ellen Tauscher, a former member of Congress from California who worked for the State Department under Clinton, offered similar support.
In hindsight, "some mistakes were made," Tauscher said Sunday on Fox News.
Officials can "quibble about whether [some emails] should be reclassified" now, she said, but Clinton has repeatedly said she didn't send or receive information that was classified at the time it was sent or received.
As the Clinton campaign rolled out its defense, Republican front-runner Donald Trump said he didn't think Clinton's campaign could survive the controversy.
In a telephone interview with Stephanopoulos, Trump said Clinton is "very damaged ... because of the email thing."
"Assuming she could get over that, which I just don't know how she possibly can," he said the GOP will have the upper hand whether Clinton or Vice President
Trump took aim at one Republican rival, Wisconsin Gov.
"I like him very much, but his state has not performed well," Trump said. "People want to see real change, not Obama change. ... They want to see great change."
Walker told Stephanopoulos that Trump is parroting the "talking points of the Democrats."
"Our roads actually are better, our schools are better," he said. Those arguments "didn't work in the past, they're not going to work now."
But the two agreed on the Clinton email mess. It qualifies her, Walker said, to be "deceiver in chief."
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