Hillary Clinton earned 50 percent to Donald Trump's 41 percent. | Getty Poll: Clinton leads Trump by 9 in Pennsylvania

On the night she is set to accept the Democratic nomination in Pennsylvania's most populous city, Hillary Clinton holds a 9-point lead over Donald Trump in the latest Suffolk University survey, in no small part thanks to a strong performance in the Philadelphia metro area.

In a head-to-head matchup with the Republican nominee, Clinton earned 50 percent to Trump's 41 percent, with 8 percent undecided, said the survey, released Thursday. The 9-point margin is the same shown by an NBC News/Wall Street Journal/Marist poll conducted earlier in July, which had Clinton at 45 percent and Trump at 36 percent.

Although the Democratic nominee has won every presidential election in Pennsylvania dating back to Bill Clinton in 1992, Trump has campaigned heavily in the state, putting it on the map as a top target. On Wednesday, both Trump and his running mate, Indiana Gov. Mike Pence, stumped in Vice President Joe Biden's hometown of Scranton.

Clinton offset Trump's advantages in the western and central parts of the state with a large lead among southwest Pennsylvania and Philadelphia-area voters.

When Clinton and Trump were matched in the poll against Libertarian nominee Gary Johnson and Green Party candidate Jill Stein, Clinton's margin over Trump was the same, at 9 points — 46 percent to 37 percent. Johnson earned 5 percent, while Stein took 2 percent and 9 percent were undecided among those candidates.

The telephone survey was conducted Monday through Wednesday, surveying 500 likely voters with an overall margin of error of plus or minus 4.4 percentage points.