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Sens. Jeff Flake, Bob Corker and John McCain now make up an informal caucus

The Senate has 52 Republican senators making their would-be opposition significant

(CNN) —  

When Arizona Sen. Jeff Flake announced on the Senate floor Tuesday he wouldn’t seek re-election, Sens. John McCain and Bob Corker – two Republican senators who had already defied the President – were there on the floor, sitting side by side across the aisle from Flake.

“I would be better able to represent the people of Arizona and to better serve my country and my conscience by freeing myself of the political consideration that consumed far too much bandwidth and would cause me to compromise far too many principles,” Flake said winding down his speech.

In the moments after, McCain and Corker rose to applaud.

Flake’s decision not to run for re-election will have electoral repercussions in Arizona where the GOP is now scrambling to find a new candidate to run in his stead. But, Flake’s decision not to run leaves him unencumbered for the next 14 months in Washington: free to speak out or even vote against Trump’s agenda if he disagrees without any fear of retribution. Flake also brings the number of ardent Trump-defying Republicans to three in the US Senate, a magic number that is enough to block even simple majority votes in the Senate, where Republicans have 52 members.

It’s still unclear whether Flake, Corker or McCain would stand in the way of agenda items like tax reform, which they’ve been pushing themselves for years, or merely use their microphones to sound the alarm on Trump’s governing style. In an interview Wednesday morning, Flake warned he was unleashed now to speak out against legislation or governing tactics in a way he even admits he wouldn’t have been free to do if he were running again.

“I think it is significant,” Flake said. “I mean, I don’t expect to be voting differently than I would before, but certainly on this tax bill for example, I know that a lot of us are concerned about the debt and deficit and want to make sure that this is actually tax reform and not just a tax cut so I think it’s significant. I do.”

Flake is just the latest to openly declare his opposition to Trump. McCain made his stand in July when cast the deciding vote against legislation to repeal Obamacare – Trump’s No. 1 agenda item – because the bill had been shoved through Congress without going through so-called regular order. Corker – once considered a serious contender to be Trump’s secretary of state – has had especially sharp barbs against Trump in the weeks since he announced he wouldn’t run for re-election.

Donald Trump and Bob Corker: A timeline

Corker told CNN’s Manu Raju Tuesday that Trump’s legacy be “the debasing of our nation, the constant non-truth telling, just the name-calling.”

The reality remains that Corker, Flake and McCain, no matter their frustrations with the President, are still Republican senators. They aren’t expected to vote against GOP proposals like tax reform that have been on their own legislative wish list for decades just for the sake of embarrassing Trump. But, that doesn’t mean that the senators will feel pressure to vote for just any plan. Corker has already made it clear that he won’t support any tax bill that adds “one penny” to the deficit. He’s argued that the GOP must eat their “spinach” and close beloved tax loopholes to pay for lowering tax rates. And, McCain has insisted on “regular order,” a process that includes hearings, mark-ups and open debate on the tax bill.

Corker warned Wednesday that tax reform was GOP’s agenda item, not Trump’s and that if Trump knew what was best for him, he’d stay out of the way.

“Remember, this is what Republicans in Congress have wanted for a long, long time. This has nothing to do with the President. The President will sign it. Other than that, this is an effort that Congress needs to succeed at and we all need to lock arms … and show the intestinal fortitude to fight off I don’t know how many hundreds of special interest groups that will descend upon the Hill,” Corker said.

But, taxes are just the beginning. Corker and McCain, chair the Senate foreign relations and armed services committees respectively, among the most powerful in the Senate. And, both can use their committees, to check Trump’s executive powers when it comes to the world stage. Corker is expected to play a pivotal role in upcoming negotiations on the Iran deal. And McCain has already threatened to issue subpoenas if he has to in order to get answers on what happened when ISIS-affiliated soldiers ambushed US forces in Niger.

With Flake’s announcement Tuesday, Trump now faces three formidable foes in the Senate. Even if the members don’t stop legislation, their criticisms of Trump will be enough to move news cycles and disrupt Trump’s agenda.

On Tuesday, for example, Trump’s originally scheduled visit to Capitol Hill on Tuesday was supposed to present an opportunity for the GOP to display unity on tax reform. Instead, it was Corker’s attacks and Flake’s blistering speech that dominated the news.

Still, GOP rank-and-file members say they hope that the newly emboldened senators won’t block the party’s efforts on key agenda items or distract from their legislative work.

“They’ll represent the people back home. That’s their first responsibility,” said Sen. David Perdue, a Republican from Georgia. “I expect them to act in a professional manner. I expect they will.”

Rep. Mark Meadows, a close ally of Trump’s and the leader of the House Freedom Caucus, had this advice.

“Real patriots let their criticism and their vote go on different tracks,” he said.

CNN’s Ted Barrett contributed to this report.