For elections to the Senate in the national constituency, political parties or other movements and groups run single lists, with a number of candidates not exceeding the total number of seats to be filled. The current electoral system, adopted in 2003 and modified in 2009 and 2015, requires party lists to pass a 3% threshold in order to obtain representation. For the 2006 and 2010 elections, the threshold was set at 2%, before being raised by the 2009 reform to 3%.