Samuel L Jackson's foul-mouthed Obama ad

Although not quite matching the star-studded line-up of his 2008 campaign, Obama can still count on some high-level Hollywood support.

Although not exclusively Democratic - Republican supporters include an assortment of 1980s action movie stars, and (surprisingly) both Vince Vaughn and Adam Sandler - many of Hollywood's leading lights tend to sit in the blue camp.

And come election-time, they get wheeled out en masse. From Scarlett Johansson at the Democratic National Convention, to this latest video from the Obama campaign...