Historical clue formulations

• Anchor — 2020-07-18
• Chief support — 2019-12-09
• *Chief source of support — 2019-06-03
• Primary supporter — 2015-03-10
• Bulwark — 2008-08-20
• Bread and butter, so to speak — 2003-11-26
• Chief support — 2002-03-28
• Bulwark — 1996-03-10