Las Vegas, a city that practically mints money — especially for those who own a hotel or casino — is a favorite destination for Republican presidential nominees scratching for major donations.

Donald J. Trump, who last visited in June, has his name bolted to the skyline 64 stories up, on his hotel faced in golden glass.

But Las Vegas is also catnip for Democrats, with its thousands of unionized hotel and construction workers. Hillary Clinton will campaign there on Thursday at the local chapter of the International Brotherhood of Electrical Workers, which recently endorsed her.

The state is similar to two others in the interior West, Colorado and New Mexico, which have traditionally been seen as battlegrounds, but which seem to be eluding Mr. Trump’s grasp because of their sizable blocs of Hispanic voters, who in polls remain hostile to the Republican nominee.