INDIANA, United States (AFP) — Donald Trump dismissed early voting Monday as “stupid” but nevertheless encouraged voters in Pennsylvania to cast ballots as soon as possible, as he vowed if elected United States (US) president to repel a migrant “invasion” of the battleground state.

“If we win Pennsylvania, we win the whole thing. It’s very simple,” he said of what is perhaps the biggest prize among the swing states likely to determine whether Trump or Democrat Kamala Harris wins the White House on November 5.

“Go out, make a plan to vote early, vote absentee or vote in-person on election day,” he said.

Trump reminded the crowd in the town of Indiana, in western Pennsylvania, that early voting in the state rolls out over the next two weeks.

“You can start right away, you know that right? Now we have this stupid stuff where you can vote 45 days early,” Trump said, as he again floated suspicions about early voting in 2020, when he lost Pennsylvania and the election to Joe Biden.

“I wonder what the hell happens during that 45 (days),” he said. “What happened the last time was disgraceful, including right here. But we’re not going to let it happen again.”

Trump has routinely said on the campaign trail he prefers one-day voting. But in a bid to neutralise the advantage Democrats have had in recent elections with early voting, his campaign has been encouraging Republicans to cast ballots before election day.

Trump also spent much of his rambling, 90-minute address on immigration, the hot-button issue around which he has based his campaign. He reprised his dark imagery of “murderers” and other “evil” migrants pouring across the border and taking over communities.

“If Kamala Harris wins this election, she will flood Pennsylvania’s cities and towns with illegal migrants from all over the world, and Pennsylvania will never be the same,” he claimed.

“We’ll end the invasion of small-town Pennsylvania and we will end the destruction of America.”

Trump portrayed rival Harris, the current vice president, as the instigator of a migrant crisis, saying she “flies in thousands and thousands of migrants from the most dangerous places on Earth” into American communities.

He mentioned Springfield, the Ohio city where he and other Republicans have repeated unfounded and racist claims that Haitian immigrants there have been eating residents’ cats and dogs, and also singled out Charleroi, a Pennsylvania town of 4,000 people which he falsely claimed has seen a 2,000 per cent increase in population in recent years.

US media have reported that the town’s population has in fact grown by 700-2,000 new immigrant residents.

Trump also touched on another issue important to Pennsylvania voters: energy, and more specifically fracking, a form of natural gas extraction that Harris once opposed, but now says she supports.

“If anybody here believes that she will let your industry continue, like fracking, you should immediately go to a psychiatrist and have your head examined,” Trump said, to cheers.