No one knew which way Senate Minority Leader Mitch McConnell was leaning earlier this week as a vote to advance the much-ballyhooed bipartisan infrastructure bill approached. The Kentucky senator is famous for not tipping his hand. So when he made it known Wednesday that he would give the thumbs-up to the bill — one that is a signature legislation piece for President Biden — even his closest Republican colleagues were surprised.

On the Senate floor, McConnell let it be known he would support pushing the bill forward, as long as the legislation that comes to a final vote was the agreement the bipartisan group negotiating the bill — not something that is written by Senate Democrats.

South Dakota Senator John Thune, the GOP whip and a close McConnell ally, said this to Politico:

“The leader just kind of let everybody do their own thing, and they did. And he did his own thing.”

There is no doubt that it was surprising to see the Kentucky Republican support one of the Biden Administration’s top priorities. The legislation, which has been on life support several times along the way and remains on unsteady ground, would inject $550 billion in new spending to rebuild America’s roads, bridges, public transit as well as broadband across much of the country.

The fact that McConnell, who often seems to revel in being known as “the Grim Reaper” of the Senate for his knack for killing Democrat-sponsored legislation and who has publicly said his priority is to block the Biden White House, would put his weight behind this bill speaks to its importance. It also underscores just how much the infrastructure has split a GOP conference that is typically more united under McConnell.

More from Politico:

McConnell’s brand is lockstep GOP opposition in the face of Democratic government. And he faces anything but unity in the days ahead. Just 18 of 50 Senate Republicans supported moving forward on the infrastructure accord, with every presumed 2024 presidential contender voting no. Only two members of McConnell’s primary six-person leadership team voted positively on the bill.

Alaska Senator Lisa Murkowski, part of the team putting the bipartisan bill together, saw McConnell’s move as a sign that he recognizes the dysfunction that has plagued Congress in recent years.

Senate Democrats were certainly caught off-guard by McConnell’s choice, with Hawaii Senator Brian Schatz acknowledging he’ll gladly admit to being mistaken if McConnell continues to support the bill.

Most D.C. observers see this as just another calculated decision by a politician whose ability to read the Washington tea leaves is unmatched. McConnell may recognize that blocking every bit of Democratic legislation — especially one that has such incontrovertible benefits such as infrastructure — could hurt the GOP more than help it down the road. In particular, he may fear that blocking this bill would help sway Democrats Joe Manchin and Kyrsten Sinemato moving off their firm opposition to removing the Senate filibuster.

Of course, McConnell also has concerns within his own party, and not just from Senators opposing the bill. Former President Trump blasted the bipartisan bill within minutes of it being advanced and threatened any Republicans who voted for it.