Consider this an open thread for following other Democratic defections, of which I assume there’ll be more before the end of the day. Mark Udall was the first to lower the boom:

In light of IG report & systemic issues at @DeptVetAffairs, Sec. Shinseki must step down: http://t.co/7zfNxqQMZa

— Mark Udall (@MarkUdall) May 28, 2014

John Walsh, who was appointed a few months ago after Max Baucus left the Senate to become ambassador to China, followed Udall by calling for Shinseki’s firing later this afternoon. What do those two guys have in common? Right — they’re both facing the voters in November with a very real chance of losing. Walsh trails by double digits in deep-red Montana and Udall’s clinging to a narrow lead against a strong challenger in Cory Gardner in purplish Colorado. What you’re seeing here, simply, is two vulnerable incumbents deciding after today’s IG report that Shinseki is irredeemably radioactive. More will follow. The next to fall, presumably, is Mark Pryor, who not only has the same reelection problem as Udall and Walsh but who’s facing a Republican in Tom Cotton who’s a veteran himself. The Cotton attack ad writes itself: “When I got home from Iraq, I trusted that the VA would be there for me and my friends. That trust has been betrayed. And Mark Pryor’s done nothing about it.” Pryor knows it’s coming too, which is why he signed on as a co-sponsor of Marco Rubio’s VA Accountability bill this afternoon. He’ll drop the hammer on Shinseki soon enough. And by “soon enough,” I mean “possibly before dinner.”

For what it’s worth, after more than five years of inaction, this is suddenly a very high priority for Shinseki:

“I respect the independent review and recommendations of the Office of Inspector General (OIG) regarding systemic issues with patient scheduling and access. I have reviewed the interim report, and the findings are reprehensible to me, to this Department, and to Veterans. I am directing that the Phoenix VA Health Care System (VAHCS) immediately triage each of the 1,700 Veterans identified by the OIG to bring them timely care.

“I have already placed the Phoenix VAHCS leadership on administrative leave, and have directed an independent site team to assess scheduling and administrative practices at the Phoenix VAHCS. This team began their work in April, and we are already taking action on multiple recommendations from this report.

“We will aggressively and fully implement the remaining OIG recommendations to ensure that we contact every single Veteran identified by the OIG. I have directed the Veterans Health Administration (VHA) to complete a nation-wide access review to ensure a full understanding of VA’s policy and continued integrity in managing patient access to care. Further, we are accelerating access to care throughout our system and in communities where Veterans reside.

A White House spokesman this afternoon told the press that Denis McDonough briefed Obama on the IG report and that The One found it “extremely troubling” — again, a good five years too late. Remember, by the IG’s own count, no fewer than 18 reports about problems in VA scheduling have been issued by their office since 2005. Obama campaigned on fixing the problem. And today he’s “troubled.”

Exit question: Let’s start a pool. What time does Pryor abandon ship? Specify your answer to the exact minute, please.

Update: Annnnnd no sooner did I set this post to publish than Ed pinged me with news of a new Democratic defection. Kay Hagan, another weak red-state incumbent in deep trouble this fall, heads for the lifeboats:

Sen @kayhagan says it "is time for (Shinseki) to step aside and allow new leadership to take the helm at the VA to correct these failings"

— Jake Tapper (@jaketapper) May 28, 2014

Update: Most House Democrats are sticking with O so far, but not all:

Rahall & Garcia too MT @frankthorpNBC House Ds Calling on Shinseki to Resign: Scott, Barrow, Peters, Tim Ryan, Braley, Barber, Sinema, Nolan

— Matt Fuller (@MEPFuller) May 28, 2014