A key supporter of a U-S constitutional convention says it would be a “release valve” because Congress refuses to control the federal budget. Two Wisconsin committees held a public hearing Tuesday on bills to make the Badger State the 30th to call for the nation’s first constitutional convention. At least 34 states would have to call the convention, and Delafield Senator Chris Kapenga says it’s needed to pass an amendment demanding a balanced federal budget. But Senate Democrat Kathleen Vinehout of Alma says it would also open the process to changing “other rights we hold so dear” — like free speech. The Wisconsin bills demand that the convention be limited to the balanced budget amendment, and Oshkosh Assembly Republican Mike Schraa says the movement could result in Congress finally taking action without the need for a convention.