The millions of signs that Americans place on their lawns during election season are increasingly being vandalised or removed by disgruntled neighbours, a sign of the acutely hostile political climate.

After signs expressing support for Democratic candidate Joe Biden disappeared twice from a road outside Newtown, Pennsylvania, Gayle Share-Raab covered the next one in vaseline and glitter to try to deter the thief, but to no avail.

Jack Worthington was fed up with his big, plastic Donald Trump signs vanishing. So he built his own, with plywood and screws as reinforcements. They are still up, for now.

Across the country, there are reports that signs are being stolen or damaged at an unprecedented rate.The phenomenon is common every election year but appears to have taken off in 2016 before accelerating this year.

“I've never seen it like this in my lifetime,” said Share-Raab.

Besides petroleum jelly, other means homeowners use to deter unwelcome visitors include grass-colored string, a coat of hair gel or honey, and a perimeter of barbed wire or even dog poop.

Steve Cickay, a Democratic activist, estimates that roughly 2,000 or 3,000 Biden signs have been “stolen, thrown in the woods or defaced” in Bucks County, where Newtown is located.

Worthington believes he has lost about a quarter of the 4,000 small pro-Trump signs that he has installed.

He sometimes manages to fix the larger ones, like the time someone altered a Trump-Pence sign into an obscene slogan on the grounds of a female 96-year-old Republican farmer.

“If they spray paint them, I'm OK with that, because it just makes the other side look really bad,” says Worthington.

His father, Jim Worthington, founder of the People4Trump organisation, says Republicans don't steal Democrats' signs because they “believe in law and order”. Cickay, a member of the Newtown Democrats, scoffs at that suggestion.

“They're supposed to be the champions of law or order and yet they are encouraging breaking the law,” he says.

Newtown police say they receive several complaints a week but have yet to arrest anyone.

“The police feels like if they go after these folks they're going to look like they're picking sides. They prefer not to confront it,” says Jim Worthington.

'Arms race'

According to CCTV images collected by locals, the thieves are often fairly young men in shorts and sneakers acting on impulse, rather than with premeditation.

At his workshop in Bucks, a key county in the battleground state of Pennsylvania, the younger Worthington is busy making additional signs that he will plant in the run-up to Tuesday's election day.

Hillary Clinton won the county by less than a point in 2016 and its representative in the House is a Republican.

“Trump supporters feel like they're pointed out and ostracised ... so when the signs are up, it gives other supporters strength,” says Jim Worthington.

“When you see Trump signs you want to see signs for your candidate,” says Biden supporter Share-Raab.

Cickay likens it to “an arms race”, the smaller signs priced between two and four dollars each.

“In a way, it could be seen as a waste of money, especially when it gets out of hand,” he says.

Both camps see a deliberate strategy in the theft and damage of signs.

“They want to create the illusion that there's not that much Biden support in our county,” says Cickay.

Slayers of Trump signs are trying to “intimidate” voters, according to Jim Worthington, who doesn't rule out that supporters of Biden are damaging their own signs to point the finger at fans of Trump.