Senate Minority Leader Mitch McConnell walks to the Senate floor before the vote to begin work on a bill that includes aid for Ukraine, Israel and Taiwan, at the US Capitol in Washington, DC, on February 9, 2024.

Mitch McConnell had long prided himself on maintaining GOP unity during his 17-year tenure as Senate GOP leader.

That’s hardly the case anymore.

As his party has descended into a bitter dispute over immigration, his small contingent of foes within his conference has grown louder and much more outspoken, driven in large part over the border, Ukraine and – in no small part – Donald Trump.

In the past, GOP grumblings about McConnell were mostly done in private. Now they’ve spilled into public view as the Kentucky Republican heads into what could be his final year as leader.

At least five of his detractors have openly called for new leadership in recent days – even holding a news conference last week demanding his ouster, a move that would have been unthinkable in years past but underscores how the 118th Congress has been unquestionably McConnell’s most tumultuous period atop his conference.

“There’s a lot of division even over Mitch remaining leader,” said Sen. Kevin Cramer, a North Dakota Republican who supports McConnell, noting his foes who have gone public are the same ones who were critical of him in the past. “Mitch could argue that he’s got a followership problem as much as they have a leader problem.”

Asked if McConnell should run again for leader, Cramer said: “He’s the world’s greatest vote counter, and I don’t know what he might want to do. What I can’t imagine is why he would want to run again.“

During his reign in the Senate, McConnell has been lauded by his Republican allies and Democratic foes alike as a tactician calculating ways to stay ahead of his opponents and always with an eye on the next election. On Friday, his backers were quick to point out more of those attributes as he helped woo former Gov. Larry Hogan into the US Senate race in Maryland, suddenly turning a safe Democratic seat into a competitive one, a major boost for the GOP.

“That was a huge victory for the good guys,” McConnell, whose big-spending super PAC is once again poised to be a major player in key Senate races, said Friday. “To have a genuinely competitive candidate in a blue state like that is a big development.”

But what has caused the most tension in the ranks: McConnell’s long campaign to unequivocally support Ukraine with billions more in US dollars, an issue that has now left the 81-year-old in the minority of his conference at a time when Trump, once again, is driving the direction of his party and has openly called on the GOP to dump him as leader.

Airmen with the 436th Aerial Port Squadron use a forklift to move 155 mm shells ultimately bound for Ukraine, on April 29, 2022, at Dover Air Force Base in Delaware.

“McConnell’s problem is that he doesn’t actually talk to or listen to voters or his members. … I don’t think I’ve had a conversation with McConnell in over a year,” said Sen. Josh Hawley, a Missouri Republican who voted against McConnell as leader and has emerged as one of his leading critics in the conference. “The guy, he’s completely bubble-wrapped.”

The debate over McConnell’s leadership has also been a point of contention in closed-door GOP conference meetings over the last month as members have pointedly questioned him and sparred with colleagues over the best strategy on immigration – sessions described by senators as “robust,” “vigorous” and “ugly.” McConnell’s critics see an opening to seize on his leadership as they view his position on Ukraine as incongruent with the majority of Republican voters back home.

“I think it was a huge mistake for him to be championing sending money to Ukraine at the expense of trying to figure out our border problem first,” said Republican Sen. Rand Paul, a fellow Kentuckian who used to be closely aligned with the GOP leader but who has been sharply at odds with him in recent years.

Yet what’s angered McConnell’s allies and inner circle is this: McConnell selected GOP Sen. James Lankford of Oklahoma to cut a deal to impose new restrictions on the US border because Republicans themselves had demanded action on the border before green-lighting more aid to Ukraine.

Lankford, with the help of McConnell, then cut a bipartisan deal after nearly five months of negotiations and forced the White House to make key concessions. But Republicans – at the urging of Trump – rushed to kill it, even before fully reviewing the details.

Ultimately, McConnell chose to vote against proceeding to the very deal he cut, with just four Republicans supporting moving forward with it.

“I followed the instructions of our conference who were insisting that we tackle this in October,” McConnell said last week when asked about his handling of the episode.

Others said there was no way around Trump’s opposition, which ultimately led House GOP leaders to come out against the border deal that they argued was too weak. And once top House Republicans vowed to kill it, GOP senators said there was no point in moving ahead.

“Donald Trump wanted the border bill to be killed, and I think the base of our party is happy with that,” said Sen. Mitt Romney of Utah, one of the four Republicans who voted to advance the border package. “We did what Donald Trump wanted.”

With McConnell’s backing, the Senate is now taking a different approach. McConnell and 16 other Senate Republicans voted to advance a $95.3 billion aid package for Ukraine, Israel and Taiwan – without any new border policy measures – and the measure is expected to pass the chamber by the middle of this week. Two of McConnell’s potential successors, Sens. John Cornyn of Texas and John Thune of South Dakota, voted to advance the aid package – while a third, Sen. John Barrasso of Wyoming, voted to block it.

“This is about rebuilding the arsenal of democracy and demonstrating to our allies and adversaries alike that we’re serious about exercising American strength,” McConnell said, defending his position.

Yet McConnell’s critics are now blaming him.

“Horrible,” Sen. Ron Johnson of Wisconsin, who has called on McConnell to step aside, said of his handling of the talks. “He’s mishandled this.”

Florida Sen. Rick Scott, who unsuccessfully challenged McConnell for leader after the 2022 midterms, said of Lankford: “He’s been sent on a suicide mission.”

“(McConnell) engineered a process that was destined to fail. The only outcome it was likely to produce was a bill that failed to secure the border and simultaneously provided political camouflage for Democrats,” said Sen. Ted Cruz, a Republican from Texas, who called for McConnell to step down last week. “McConnell just effectively gave the largest in-kind contribution to the Democratic Senate Committee in history.”

Sen. Ted Cruz, a Republican from Texas, leaves a Republican Senate conference meeting at the US Capitol ahead of votes on February 7, 2024 in Washington, DC.

Asked about Cruz, who has long sparred with the GOP leader, McConnell quipped: “I think we can all agree that Sen. Cruz is not a fan.”

On the floor Thursday, Cruz approached McConnell and engaged with the leader after the Texas Republican had assailed him earlier in the week. McConnell, cracking a reserved smile on his face and holding his hands together in front of him, nodded periodically.

A source familiar with the interaction said: “Cruz was actually trying to make up with the leader” in that conversation. A Cruz spokesperson declined to comment on the conversation, as did McConnell’s.

“Sen Cruz talks every day with his colleagues, and his conversations with fellow senators are confidential,” the Cruz spokesperson said.

McConnell’s possible successors split on Ukraine aid

McConnell has not divulged whether he will try to stay as leader after the 2024 elections, committing so far only to remain in the spot through the end of this Congress. Yet many Senate Republicans told CNN that McConnell would likely have the support to remain as leader if he chose to hang on.

“Mitch is a guy, year in, year out, who has been able to kind of bring us all together,” said Sen. Mike Rounds of South Dakota.

Rounds said of the battle over immigration and Ukraine: “This is one of those more challenging ones, that’s all, and this is a really important issue that a lot of us feel very strongly about.”

Asked if he could sustain support if he ran again for leader, Rounds argued, “There’s no question in my mind that as of right now, today, Mitch is the leader, and he would have more than a majority of support of the conference.”

McConnell’s allies said the GOP leader knew full well he would endure backlash over his handling of Ukraine – given where the Trump wing of the party stands on that issue.

“He’s always had a light touch, but as soon as Tucker Carlson and Donald Trump said we don’t want to support Ukraine, you are going to see a lot of Republicans run to get behind them,” Romney said.

But not everyone is as confident McConnell will stay on – especially if Trump becomes president – given that the two haven’t spoken in more than three years and McConnell has stood by his withering criticism of Trump over the January 6, 2021, attack on the US Capitol.

Sen. Tommy Tuberville, a Republican from Alabama and close Trump ally, said that “everybody” has concerns about McConnell’s handling of the talks. “The direction we took this – we gotta have leadership.”

“There will be a lot of talk about it when we come back,” said Tuberville, who backed McConnell in the past. “I promise you.”

CNN’s Morgan Rimmer contributed to this report.