The presumptive Democratic nominee Hillary Clinton holds a small 5-point lead over Republican challenger Donald Trump, according to the June CNBC All-America Economic Survey, with a large chunk of the voting public remaining undecided.

The poll of 801 registered voters conducted June 11-14 shows Clinton with a 40 percent to 35 percent lead, but the poll's margin of error is plus or minus 3.5 percentage points. Pollsters for CNBC say the survey shows a tight race with 25 percent undecided, including 14 percent who right now choose "neither" candidate.

Hillary Clinton and Donald Trump Reuters; Getty Images

"It's the hallmark of a campaign with high negatives around these candidates," said pollster Micah Roberts with Public Opinion Strategies. The poll was conducted by POS from the Republican side and Hart Research Associates from the Democratic side. But both pollsters pointed to one group that could increase Clinton's margin. The survey shows that 20 percent of voters who had supported Democrat Bernie Sanders currently choosing neither candidate. "I've seen nothing to suggest that Sanders supporters won't break in favor of Clinton,'' said Jay Campbell, Hart Research's senior vice president. He points out that Sanders supporters who have made their decisions back Clinton about 6 to 1.

In other findings: Americans are divided on which candidate is best for the economy, 39 percent to 38 percent in favor of Clinton. They are also tied on who is best for dealing with terrorism, and who is best for a person's personal financial situation and for small business. Clinton holds leads on who is best for health care, trade, immigration and the lower and middle classes. Trump leads on who would be best for stocks, regulating Wall Street and banks, dealing with the budget deficit, large companies and the wealthy Sixty-two percent, including 41 percent of Republicans, say Trump should release his tax returns. Fifty-eight percent say a Trump presidency would make America's standing in the world worse, compared with 38 percent for Clinton. The horrific attack in Orlando, Florida, occurred in the middle of the survey but pollsters said they found little effect on presidential choice. The economy and unemployment ranked as the top election issue for Americans both before and after the massacre, chosen by 26 percent of Americans compared with 20 percent who chose foreign policy, world leadership and combating terrorism. But the foreign policy category did rise by 6 points from 15 percent to 21 percent after the attack.

