After weeks of bad news for Hillary Clinton, Donald Trump has caught up to the presumptive Democratic nominee, and the two candidates are now tied at 40 percentage points each, according to a new CBS/New York Times national poll.

Clinton led Trump by 6 percentage points last month, but she dropped 3 points and Trump gained 3 points since the previous poll.

The shift appears to reflect independents leaving Clinton for Trump. The poll showed independent voters were virtually split even last month, but Trump now leads by 12 points.

Those changes could be the result of Clinton's private email scandal. After FBI Director James Comey said Clinton sent and received classified information on her private, nonsecure server, Clinton's favorable rating plunged below Trump for the first time this campaign season.

Approximately 28 percent of voters viewed Clinton favorably while 30 percent of voters viewed Trump favorably. Both candidates were viewed unfavorably by 54 percent of respondents.

At similar points before the conventions in previous election cycles, CBS noted, President Obama led Mitt Romney by 1 percentage point in 2012 and had a 3-point advantage on John McCain in 2008. The new poll was compared to August polls from 2012 and 2008 because the conventions were held later in those years.

While it's still early to suggest the CBS/NYT poll is predictive of November's outcome, it shows Clinton's problems are mounting as both parties head into the conventions this month.

The CBS/New York Times survey polled 1,600 adults, including 1,358 registered voters, from July 8-12. Interviews with respondents were conducted in English and Spanish, and the survey has a plus or minus 3-point margin of error.