sentences:  In recent years, historians such as Harry Jaffa, Herman Belz, John Diggins, Vernon Burton and Eric Foner have stressed Lincoln's redefinition of "republican values".As early as the 1850s, a time when most political rhetoric focused on the sanctity of the Constitution, Lincoln redirected emphasis to the Declaration of Independence as the foundation of American political values—what he called the "sheet anchor" of republicanism.The Declaration's emphasis on freedom and equality for all, in contrast to the Constitution's tolerance of slavery, shifted the debate.