Mitch McConnell is confronting a dynamic this week he hasn’t faced before during Joe Biden’s presidency: A fractured Republican Senate caucus.

With the upper chamber beginning to debate the merits of $550 billion in new infrastructure spending, McConnell has aligned himself with a minority of 17 GOP senators who voted with all Democrats to proceed with considering the legislation that was only finalized on Sunday.

It’s an unlikely position for the Kentuckian, who prizes Republican unity and is known for his ability to read the desire of his members. And it’s genuinely surprised liberals, who have been highly skeptical of McConnell’s willingness to permit a significant deal with Democrats.

On Monday, McConnell called the bipartisan package of roads, bridges, waterways and airports “necessities” for the country.

But the amendment process that will unfold on the Senate floor over this week will determine the extent of McConnell’s bipartisan enthusiasm.

While Republicans say McConnell truly believes infrastructure would benefit the country and enhance its global competitiveness, the leader won’t fully settle on supporting final passage of the bill until the amendments unfold.

That’s where things could get tricky.

Republican leaders are stressing they want a robust amendment process for the 2,700 page bill that isn’t rushed.

“Our full consideration of this bill must not be choked off by any artificial timetable that our Democratic colleagues may have penciled out for political purposes,” McConnell said on Monday.

But Senate Majority Leader Chuck Schumer would like a final vote on the sweeping bill to take place this week and is urging a faster process.

“I hope that we can use our time in the Senate efficiently,” Schumer said. “Let’s start voting on amendments. The longer it takes to finish the bill, the longer we’ll be here.”

On Monday afternoon, Republicans were still finalizing the exact number of amendments they will bring to the floor. But areas where they’d like alterations include climate provisions and funding for the Keystone XL and Nord Stream 2 pipelines, the Davis-Bacon Act involving wages for laborers, broadband technology and perhaps most crucially, the financing of the plan.

“There are concerns over the legislative language,” said Sen. Marsha Blackburn, a Tennessee Republican who is working on an amendment around broadband provisions that she says currently include “red-lining and digital discrimination.”

Blackburn is one of the 32 Republicans who opposed moving forward with the bill, and conservatives are only beginning to pick apart the gargantuan bill to expose flaws.

Stephen Moore, a conservative economist who advised former President Donald Trump, claimed that “only 1 in 4 infrastructure dollars goes to roads, bridges or airports.”

“Out of almost $600 billion in spending in this ‘bipartisan deal,’ less than $150 billion is for that!” Moore wrote.

Laura Ingraham, the primetime Fox News host, amplified a Breitbart article highlighting a portion of the bill that says states and metro areas should develop carbon reduction strategies.

Republican Sen. Josh Hawley of Missouri flagged a sentence defining gender identity as a way to demonstrate hidden provisions that haven’t yet seen the light of day.

But it might be the case that the bill, which already has significant Republican support, is too big to fail — meaning there’s so much money spread around to different state projects, it’ll survive by sheer size and force.

The current bill includes $110 billion for roads and bridges, $66 billion for railways, $55 billion for water and $39 billion for public transportation.

McConnell appears to want to allow the more conservative members of his caucus — including those on his leadership team — to have the chance to tweak language, trim costs and adjust pay-fors, before signing on to legislation some of his key allies, like Sen. Rob Portman of Ohio, shaped.

Many are unlikely to get onboard, even with substantive amendments.

“With this pricetag, I don’t know if there is” a way to get to yes, Blackburn said.

That’s why McConnell is already looking ahead, eager to reunite his caucus against the even larger $3.5 trillion spending bill that Schumer wants to tee up next.

On the Senate floor on Monday, McConnell devoted half of his speech to the Democrats’ next “awful package” that he guaranteed wouldn’t earn a single Republican vote.

“He can’t stop his members from voting their state and individual politics,” said Eric Johnson, an Atlantabased Republican consultant. “But he can work to prevent the social infrastructure from passing. Besides, the House may still kill this one.”

Will infrastructure matter much in the midterms? GOP operatives doubt it.