Soon after Widmer-Schlumpf's election to the Federal Council, the SVP excluded both her and the SVP's other Federal Councillor, Samuel Schmid, from the party group. Schmid, like Widmer-Schlumpf, was a member of the SVP's moderate wing, and the SVP's dominant nationalist wing reckoned them both as unrepresentative of the SVP's populist campaigns. Some SVP members demanded that Widmer-Schlumpf and Schmid be thrown out of the party altogether. However, Swiss parties are legally federations of cantonal parties, and the SVP could not expel them directly. For them to have been expelled, the party's Graubünden and Bern sections, to which Widmer-Schlumpf and Schmid belonged respectively, would have had to expel them. On 2 April 2008 the national SVP leadership called for Widmer-Schlumpf to immediately resign from both the Federal Council and the party. When Widmer-Schlumpf declined to do so, the national SVP demanded that the Graubünden branch expel her. The Graubünden section stood by Widmer-Schlumpf, and was expelled from the national SVP on June 1. On 16 June 2008, the delegates' convention of the SVP's former Graubünden branch voted to change its name to BPS Graubünden, becoming the first cantonal section of what would become the BDP. A second cantonal section was founded in Bern on 21 June 2008 under the name BDP ; the change from BPS to BDP was due to a name conflict with the extant minor partyBürgerpartei Schweiz, which has the same acronym BPS. As a result, the Graubünden branch also changed its name to BDP Graubünden. Soon afterward, nearly all of the SVP's Bern section, including Schmid, defected to the new party. Eleven other cantonal branches have been founded, predominantly in German-speaking Switzerland: Aargau, Basel-Landschaft, Fribourg, Glarus, Lucerne, Schwyz, Solothurn, St. Gallen, Thurgau, Valais, and Zürich.
BDP has one seat in the Council of States, and 3 out of the 200 seats in the National Council. Seventeen members of the Grand Council of Bern defected to the BDP from the SVP. In the 2010 election, the number of BDP councillors increased to 25, making the BDP the third-largest party in Bern, behind the SVP and Social Democratic Party Having been founded by the mass defection of the local SVP, the Conservative Democrats are also the third-largest delegation in the Grand Council of Graubünden, with 30 seats, behind the Christian Democratic People's Party and FDP.The Liberals. The BDP is also the third-largest party in the Cantonal Council of neighbouring Glarus, with ten of the legislature's sixty seats. After the BDP had lost four seats in the 2019 election and therefore lost its status as an own parliamentary group, the remaining three parliamentarians decided to join a parliamentary group together with the CVP and the EVP.