Mitch McConnell speaking at the Capitol on Tuesday. Pool photo by Rod Lamkey

The Senate seems to have a deal on virus relief — despite Mitch McConnell’s “red line.”

Over the spring and summer, Mitch McConnell repeatedly declared that he had a litmus test for any new coronavirus stimulus bill: It had to protect businesses from lawsuits from workers or customers who contracted the virus.

“We have a red line on liability,”

he said at one point.

“I won’t put a bill on the floor that doesn’t have liability protection in it,”

he said at another.

“No bill will pass the Senate without liability protection for everyone related to the coronavirus,”

he added.

But McConnell, the Republican leader in the Senate, has since erased that red line. Congressional leaders and Steven Mnuchin, the Treasury secretary, are nearing agreement on a $900 billion bill that doesn’t include liability protection.

So why did McConnell, arguably the savviest politician in Washington, fold?

The answer offers an important reminder of how the Senate really works and how it could become less dysfunctional in the near future than it has been lately.

When people talk about the Senate, they often imagine that McConnell, as the majority leader, is all-powerful and can prevent any bill he doesn’t like from coming up for a vote.

That’s not the case. Any senator can propose that a bill receive a vote. If at least 50 other senators want it to receive one, it will.

In recent decades, though, senators have voluntarily surrendered this power to their party’s leader, giving him (and, no, the Senate has never had a female majority or minority leader) a veto over what comes to the floor. The practice helps keep parties unified.

But it comes with a major downside. It makes bipartisan compromise harder to achieve.

Coalitions that could pass a bill — but that don’t include the majority leader — don’t get the chance to form.

“By stopping the legislative process before it starts, it makes compromise harder.”

James Wallner, a former Republican Senate staff member, has told me.

On the latest round of stimulus, a bipartisan group of senators changed the dynamic by making clear that they strongly favored additional aid. They did not publicly threaten to go around McConnell, but they didn’t have to. He can count to 51, and he was also worried that the two Republican candidates in next month’s Georgia Senate runoffs were “getting hammered” over the lack of a deal.

(McConnell did win a big concession as part of abandoning his red line: The proposed deal does not contain aid to state and local governments, even though the bipartisan group had included it in their earlier proposal and despite many economists favoring such aid.)

It’s possible this bipartisan deal will end up being a one-time event. But it doesn’t have to be. Senators have it within their power to find other areas of compromise next year, during Joe Biden’s presidency — even if McConnell does not favor those deals.

“In politics victory begets victory,”

Rahm Emanuel, the Democratic former House member and Chicago mayor, told me yesterday.

“The center-out governing coalition has a win under their belt.” It is a “big opportunity for Biden,”

Emanuel said.

Perhaps most intriguing, senators have the power to craft compromises regardless of which party wins the Georgia runoffs and controls the Senate.