I’ll be honest and tell you that I do not know if the U.S. Senate will ever hold a trial to determine whether President Trump should be removed from office. A lot will depend on the timing of the Office of Special Counsel wrapping up its investigation. If it takes too long to provide its evidence, the Democrats may decide that it’s better to leave Trump twisting in the wind as a weakened 2020 opponent than to make a full-court press effort to impeach him.

However, if Trump does get impeached later this year, the Senate will serve as his jurors. Most likely, the president won’t be able to rely on any Democratic votes, which means he’ll only be able to afford 19 Republican defections if he wants to survive.

If the impeachment process gets to the point that there’s real doubt about whether Trump can hold the Senate Republicans in line, it’s likely that he’d resign rather force the Senate to hold a trial. At the very least, he’d be advised that he was likely to lose and asked to do everyone a favor and leave voluntarily.

However that would ultimately shake out, the part that has always been hard to imagine is that any significant number of Republican senators would seriously consider ousting their own president. After all, Trump is still getting very high approval numbers from Republican voters.  GOP senators who have stood up to him, however haltingly, have not fared well. Consider the cases of Bob Corker and Jeff Flake.

It’s obvious that half the hurdle is convincing Republican senators that they won’t be ending their political careers if they force Trump out. But the other half of the battle is convincing them that conviction and/or removal is the correct decision.  I expect the actual report will do most of the work on that front, but there will be other factors. One is whether or not they sincerely believe that Trump is doing a bad job and is unfit for the office.

The only senator to actually endorse Donald Trump in the primaries was Jeff Sessions of Alabama. The remainder were opposed to him winning the nomination. I very much doubt that he has any more sincere support in the Senate now than he did then. Many of them blame him for losing the House. Most of them are seething about being forced into a government shutdown they did not want. But the biggest sign of their discontent so far is coming directly from their Majority Leader.

Frustrated Republicans say it’s time for the Senate to reclaim more power over foreign policy and are planning to move a measure Thursday that would be a stunning rebuke to a president of their own party.

GOP lawmakers are deeply concerned over President Trump’s reluctance to listen to his senior military and intelligence advisers, fearing it could erode national security. They say the Senate has lost too much of its constitutional power over shaping the nation’s foreign policy and argue that it’s time to begin clawing some of it back.

“Power over foreign policy has shifted to the executive branch over the last 30 years. Many of us in the Senate want to start taking it back,” said a Republican senator closely allied with Senate Majority Leader Mitch McConnell (R-Ky.).

They plan to send Trump a stern admonishment by voting Thursday afternoon on an amendment sponsored by McConnell warning “the precipitous withdrawal” of U.S. forces from Syria and Afghanistan “could put at risk hard-won gains and United States national security.”

The resolution also expresses a sense of the Senate that the Islamic State in Iraq and Syria (ISIS) and al Qaeda pose a “continuing threat to the homeland and our allies” and maintain an “ability to operate in Syria and Afghanistan.”

It’s a pointed rebuttal to the claim Trump made on Twitter in December that “we have defeated ISIS in Syria.”

Speaking on the Senate floor, McConnell said his amendment “simply re-emphasizes the expertise and counsel offered by experts who have served presidents of both parties,” a subtle rebuff of Trump’s tweets from earlier in the day mocking his intelligence advisers as “naive.”

It would be appropriate if disagreements over foreign policy are what ultimately causes the Senate Republicans to oust Trump. The primary concern with the president is that he is a pawn of a foreign power. The way this most obviously manifests itself is in his attacks on U.S. allies and western organizations like NATO and the European Union. Articles of impeachment are likely to deal with witness tampering, perjury, obstruction of justice, and a conspiracy to defraud the American public. But it Trump is actually tossed out, it will be primarily because the Senate Republicans do not trust his leadership on foreign policy.

His refusal to listen to his own intelligence experts is now causing a firestorm. I can’t think of any precedent for a rebuke like this from a president’s own party.

Trump stunned Republican senators Wednesday by lashing out at Director of National Intelligence Dan Coats and CIA Director Gina Haspel after they contradicted some of his optimistic claims about the threats posed by North Korea and ISIS. The senior intelligence officials also angered Trump by testifying that Iran is in compliance with the nuclear treaty it signed with Western powers under the Obama administration.

Trump tweeted “the Intelligence people seem to be extremely passive and naive when it comes to the dangers of Iran. They are wrong!” The president added in a follow-up tweet about Iran: “Perhaps Intelligence should go back to school!” Trump appeared to be responding to television news coverage that focused on how the testimony contradicted his views on global threats.

Exasperated Republican lawmakers quickly pushed back against the criticism, urging the president to show more restraint.

“I don’t know how many times you can say this, but I would prefer that the president stay off Twitter, particularly with regard to these important national security issues where you’ve got people who are experts and have the background and are professionals,” said Senate Republican Whip John Thune (S.D.). “In most cases I think he ought to, when it comes to their judgment, take it into consideration.”

For some reason I will probably never understand, the president seems to think it’s going to be more important for him to keep Ann Coulter and Rush Limbaugh happy than to worry about how Mitch McConnell and John Thune are feeling about his leadership. I don’t think he’s right about that.

It’s true that maintaining support among the base is key to preventing senators from throwing him out of office. But it’s far more important that he not convince those senators that he needs to be thrown out of office.

Once they decide he ought to go, it’s much harder to convince them to sweep him crimes under the rug and rally around him as their 2020 nominee.

I’ve said for a long time that the Senate Republicans don’t like Trump, have no loyalty to Trump, don’t enjoy working with him, don’t agree with his strategies, and don’t want him to be their nominee next year. The situation has grown immeasurably worse since the midterms.

They are now openly defying the president because they see him as a threat to national security. And that’s exactly what the counterintelligence investigation on Trump has been about from the beginning. So, without even seeing the evidence, they’re already convinced.

I think Trump has spoiled his jury pool, and people who remain convinced that the Senate Republicans will save him are badly underestimating how much bipartisan agreement there is at this point that Trump is captured by Putin and mentally unfit for office.

Trump’s best bet at this point is that the Mueller Report doesn’t come out until so late in the year that the primary debates have begun and everyone just agrees to fight it out at the ballot box. But, even in that scenario, Trump is likely to get challenged for the nomination by someone who is willing to express what so many are thinking.