As recently as last summer, there was a fair amount of chatter about Senate Foreign Relations Committee Chairman Bob Corker (R-Tenn.) serving as Donald Trump’s 2016 running mate. It reached the point that the Tennessee Republican felt the need to publicly and formally withdraw from consideration.

After the election, the scuttlebutt was nearly as loud about the GOP senator joining Trump’s cabinet as secretary of state.

At this point, though, it’s apparently a very good thing that Corker is not a member of Team Trump.

A prominent Republican senator delivered a stinging rebuke Thursday of Donald Trump’s short time in office, declaring he has not shown the stability or competence required for an American president to succeed. Sen. Bob Corker of Tennessee, chairman of the Foreign Relations Committee, also said Trump “recently has not demonstrated that he understands the character of this nation.” During comments to local reporters after a speech to the Chattanooga Rotary Club, Corker called for “radical changes” in how the Trump White House operates.

In the same public remarks, the Republican senator reportedly said, “The president has not yet been able to demonstrate the stability, nor some of the competence, that he needs to demonstrate in order for him to be successful – and our nation and our world needs for him to be successful, whether you are Republican or Democrat.”

That’s not the kind of rhetoric we expect to hear from a prominent GOP senator about the president from his own party – but it’s becoming progressively more common of late.

Also yesterday we saw Sen. Tim Scott (R-S.C.) tell Vice News that Trump’s “moral authority” had been “compromised” by his defense of racist activists on Tuesday. Those comments come on the heels of Sen. Jeff Flake (R-Ariz.) writing about his concerns that his party is “in denial” about the dangers Trump poses.

And at a certain level, all of this is welcome. Many Trump critics have spent months wondering aloud why more GOP officials sit in silence as the president’s erratic instability becomes more obvious, so there’s reason to be pleased when some Republicans start to speak up. Ideally, some of these GOP senators’ colleagues will soon follow their lead.

But that represents the start of the conversation, not the end.

Corker, for example, is calling for “radical changes” in how the Trump White House operates, but he didn’t explain what kind of changes he’d like to see, or just as importantly, what he intends to do if the president and his team ignore the advice.

So far this year, Corker has voted with Trump roughly 90% of the time. For Tim Scott and Jeff Flake, it’s close to 94%. Each of these senators appear to have sincere concerns about the president’s fitness for office, but we don’t yet know what, if anything, they intend to do about it – and to date, they haven’t done much.

In fairness, the Senate isn’t in session, and perhaps things will be different when lawmakers return to Capitol Hill. Maybe we’ll see bipartisan support for new checks and limits on this White House. Perhaps in the wake of Charlottesville, Corker and other Republicans see Trump in meltdown mode, and we’ll soon see fed-up Republicans challenging the administration in forceful ways.

Or maybe some GOP officials are wringing their hands, but don’t intend to do much of anything to rein in the president they see as unhinged.