Donald TrumpDonald John TrumpKoch-backed group launches six-figure ad buy against Heitkamp Anti-abortion Dem wins primary fight Lipinski holds slim lead in tough Illinois primary fight MORE says only voter fraud can prevent him from winning the swing state of Pennsylvania this November.

"The only way we can lose, in my opinion, I really mean this, Pennsylvania, is if cheating goes on. I really believe it," he said Friday during a rally in Altoona, Pa. 

Trump said law enforcement and his supporters have to be on the lookout for voter fraud to keep Trump from getting "cheated out of a win."

“That’s the way we can lose the state, and we have to call up law enforcement and we have to have the sheriffs and the police chiefs and everybody watching," he said.

"The only way they can beat it, in my opinion, and I mean this 100 percent, is if in certain sections of the state they cheat." 

Trump said he finds it “shocking” when states like Pennsylvania rule out having any voter identification regulation.

“Without voter ID there’s no way you’re going to be able to check in properly,” he said.

“I’m supposed to be a smart person,” he added. “I have yet to understand how you can’t approve voter identification at least in some form.”

Trump said voters could not afford to elect Clinton due to her similarities with President Obama.

Hillary ClintonHillary Diane Rodham ClintonKoch-backed group launches six-figure ad buy against Heitkamp Trump keeps up 'low IQ' attack on Maxine Waters GOP leaders to Trump: Leave Mueller alone MORE will be so bad for our country,” he said of the Democratic presidential nominee.

“Hillary Clinton is four more years of Obama, four more years of [the Islamic State in Iraq and Syria], four more years of higher taxes,” Trump added.

“[Obama is] the great divider. He has done a terrible, terrible job. He is grossly incompetent.”

Several polls released this week show Clinton running up a sizable lead over Trump in the swing state.

An NBC/Wall Street Journal/Marist survey out Tuesday, for example, has her leading Trump by 11 points there, while a Quinnipiac University poll published the same day found Clinton up 10 points.

Clinton leads Trump by about 10 points in Pennsylvania, according to the latest RealClearPolitics average of polls.

Clinton’s lead is smaller nationwide, however, with Trump trailing her by just over 6 points.