Voters don't seem to be all that impressed with Donald Trump's business record anymore.

Nearly two-thirds of respondents to a poll released by Bloomberg this week said they were less impressed with Trump's business expertise now than they were when he started his White House bid. Only about one-third said what they had learned about the Republican presidential nominee's businesses and business practices over the course of the campaign had made them more impressed.

That's not great for a candidate who bases much of the case for his presidency on his success in the private sector.

The poll results don't indicate why voters appear to have been dissuaded about Trump's business prowess over the past year.

Ads run by Hillary Clinton's campaign and the super PACs backing her could have something to do with it. In May, Priorities USA Action rolled out an ad titled "What a Con-Man," slamming Trump's failed business ventures, including Trump Vodka, Trump Mortgage and Trump Steaks. The Clinton camp recently rolled out "Someplace," featuring a Trump appearance on The Late Show with David Letterman discussing his foreign-made ties.

At the Democratic National Convention in Philadelphia last month, the real estate magnate's rivals assailed his business record, with some of the most cutting comments coming from former New York Mayor Michael Bloomberg. "Trump says he wants to run the nation like he's run his business. God help us," he said.

Others in the business world have sounded the alarm bells about Trump as well, including Hewlett Packard Enterprise's (HPE) - Get ReportMeg Whitman, Berkshire Hathaway's (BRK.A) - Get Report (BRK.B) - Get ReportWarren Buffett and Facebook's (FB) - Get Report Mark Zuckerberg. The outspoken opposition of some of these high-profile business figures could also be seeping into voters' consciousness.

And, of course, news stories surrounding Trump University, Trump's bankruptcies and Atlantic City have not helped the candidate's business case, either.

Despite misgivings about Trump's business acumen, those polled by Bloomberg gave Trump higher marks than Clinton on "knows what it takes to create jobs" (51% to 42%) and "would rein in the power of Wall Street" (45% to 38%). She scored higher marks on items like fighting for the middle class, temperament and getting things done in Washington.

Conducted August 5-8, this marks one of the first polls to be conducted and released after Clinton's post-convention bounce, and its results indicate the former secretary of state has a rather firm lead. Bloomberg's two-way poll gives her a six-point edge, with 50% support to his 44%. And a four-way poll including Libertarian candidate Gary Johnson and Green Party candidate Jill Stein has Clinton with a four-point edge over Trump.

Americans may not only be cooling off to Trump at the ballot box but in their shopping and travel habits as well. A recent report from Foursquare indicates traffic at Trump-branded hotels, casinos and golf courses in the U.S. has dropped significantly since he announced his White House run as well.

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