Barack Obama lost ground among certain groups of voters in the battleground state of Pennsylvania during the last week, according to a new poll.

If the Democratic Primary were held in Pennsylvania Tuesday, Hillary Clinton would beat Obama by 18 percentage points, according to the results of a SurveyUSA poll conducted exclusively for NBC 10 and three other TV stations across the Keystone State.

The poll concluded that the results were nearly identical to one of its polls released a month ago, stalling the momentum Obama picked up at the end of March.

Women and white voters barely budged and continued to support Clinton at more than 60 percent, as they have in the previous two Survey USA polls.

However, a change in men's support has negatively affected Obama.

Last week, Obama moved within 12 percentage points of Clinton, but men who flirted with the notion of voting for Obama at the end of March appear to be moving their support back to Clinton.

The poll suggests that men make up 42 percent of likely voters.

Obama also lost ground among voters between 35 and 49, down 18 points, while Clinton continued to lead among voters 50 and older.

In the Southeast section of the state, which includes Philadelphia and makes up 42 percent of likely Democratic voters, Clinton had a good week, polling above 50 percent for the first time.

Obama trailed Clinton by nine points in the critical part of the state.

In the southwestern part of the state, which includes Pittsburgh, Clinton jumped 25 points ahead of Obama. However, the Johnstown area continued to show consistent movement toward Obama, the survey concluded.

Obama also lost ground among moderates and liberals and conservatives. Clinton only fell among conservatives.

Last week's poll, which showed Obama closing the gap, was conducted in the middle of Obama's six-day bus tour through Pennsylvania, which may have helped boost his numbers.