One week after social media posts sank President Biden’s nominee for budget chief, another pick appears to be in jeopardy. More “mean tweets” and a proxy battle over Biden’s Iran policy have endangered the nomination of his pick for the No. 3 job at the Pentagon.

A single Democrat could sink the nomination of Colin Kahl to be undersecretary of defense for policy. The White House is relying on party solidarity to avoid a repeat of the fate suffered by Neera Tanden, Biden’s Office of Management and Budget nominee, whose nomination collapsed after West Virginia Sen. Joe Manchin, a centrist Democrat, said he would not support her.