What is the cause under the cause standard in a civil case?

To satisfy the cause standard, a petitioner must show that " 'some objective factor external to the defense impeded counsel's efforts' to raise the claim in state court." McCleskey v. Zant, 499 U.S. 467, 493, 111 S.Ct. 1454, 1470, 113 L.Ed.2d 517 (1991) (quoting Murray v. Carrier, 477 U.S. 478, 488, 106 S.Ct. 2639, 2645, 91 L.Ed.2d 397 (1986)). "[I]nterference by officials" is one such factor. McCleskey, 499 U.S. at 494, 111 S.Ct. at 1470 (internal quotations omitted).