The Tea Party is a decentralised, rather disorganised political movement, but one that has a very big influence on the campaign to get rid of Barack Obama. And the Republican candidates know this.
This Monday, it's the next Republican presidential debate in the United States. This one will be held in Tampa, in the state of Florida, the same place that will be used for the Republican National Convention. The debate is in part organised by the Tea Party Express, the first time the Tea Party is officially co-hosting a presidential debate.
With the Tea Party involved, you won't be surprised to hear that this time the debate will be all about the US economy, as well as a few more subjects very close to the hearts of its members: the size of government, the increase in the country's debt, and of course, jobs.
But who or what is this Tea Party Express? It's a cross-country bus tour that tries to rally its members and invites every candidate to take to its stage. A staunchly Republican organisation, it says it will endorse one candidate, when the time is right.
Our correspondents Philip Crowther and Stan de Saint Hippolyte got an inside look aboard the Tea Party Express.