Spencer Pratt Staying at Bel Air Hotel, Not Airstream Trailer

8:31 AM PT -- We asked Spencer if he has ever lived in the trailer, and he said no, adding, "I have never told anyone I lived there." However, in the campaign ad, he says squarely, "This is where I live" as he stood in front of the trailer.

Spencer Pratt has gained traction in his campaign for L.A. Mayor by showing what he says Karen Bass did to his family -- forcing them to live in a trailer after his home burned down. But TMZ has learned ... he's traded in the trailer for one of the swankiest hotels in L.A. ... but Spencer says he was forced to ditch the trailer because of death threats.

Sources with direct knowledge tell TMZ ... Spencer has been staying at the Hotel Bel-Air for more than a month. We're also told his wife, Heidi, and their kids are staying in Carpinteria, just north of L.A. So the trailer is sitting lonely.

As for the Hotel Bel-Air ... it's about as luxurious as it gets. You can't get a room for less than $1,500 a night. And check out the Swan Lake Suite -- which goes for $8,090 a night.

The Hotel is decked out with a swimming pool, plunge pools, spa, restaurants, tennis courts -- the works.

As you know, Spencer's home burned down during the L.A. fires last year, after there were multiple City failures ... from a lack of water to a hundred fire trucks that were sitting out of service.

As for why Spencer traded his Airstream for the Bel-Air ... Spencer tells TMZ he's been getting death threats and he's staying at the hotel because it has "its own armed security [and] that has become the only option."

Spencer tells TMZ, "The reality is the Bassholes and Ramaniacs are a little bit whacko, and since I destroyed them in the debate, and am surging in the polls, they are getting increasingly desperate and hostile."