The online poll shows Clinton with 50.67 percent to Trump's 44.19 percent in Monday's data. The Democratic candidate crossed the 50 percent mark in Sunday's sample for the first time since Aug. 6.
Republican Trump has declined in the poll from a peak of 49.18 percent on July 24, days after the GOP convention.
Over the course of seven days through Monday, the full sample size for the poll, Clinton added 2.15 percentage points to her total, while Trump lost .86 percent. The percentage of "others" in the poll, defined as respondents who declined to pick either candidate, dropped by 1.3 percentage points to 5.14 percent.
The UPI/CVoter online tracking poll surveys about 200 people each day, leading to a sample size of roughly 1,400 people during any seven-day span.
Because the poll is conducted online and individuals self-select to participate, a margin of error cannot be calculated. The poll has a credibility interval of 3 percentage points. This seven-day span includes data collected from Aug. 9 through Monday, when 1,445 respondents were surveyed. Of them, 1,035 identified themselves as likely voters.