Last week Donald Trump's impeachment trial went just about as well as the White House could have hoped.
Yes, there were emotive pleas from the Democratic prosecutors, excoriating the US President's "dangerous" behaviour as they lobbied hard for his removal.
But the facts were not new, having almost entirely been revealed last year, and there were few signs Republican senators, who hold the body's majority and thus the power, were swayed.
That changed yesterday. Suddenly here was a new claim, made by someone allegedly with first-hand knowledge, about an issue at the heart of the impeachment case.
John Bolton's reported account is so eye-catching as it speaks to the central question - whether Trump used nearly half a billion dollars of taxpayer money for his own benefit.
The White House put a lot of stress on the fact no one testified that they heard Trump linking the two issues. They called it one of their six core facts. Now it was being contested.
Suddenly the debate about whether to call new witnesses in the impeachment trial which has been raging for six weeks took on fresh urgency. It was no longer "shall we hear from some new people", but "should we hear evidence that allegedly contradicts a core part of the Trump team argument" - a proposition much harder to reject.
The danger posed by Bolton's testimony for the White House is the unknown. The former National Security Adviser is yet to speak publicly on the Ukraine scandal.
Yet amid the fevered mood on Capitol Hill today, the basics remained the same.
Republican voters still overwhelmingly back the President, according to polls.
The election is still less than 10 months away.
At least 20 of the 53 Republican senators will ultimately have to vote for Trump's removal for it to happen. Even with Bolton's testimony that is a mighty high bar.