Speaker of the House Nancy Pelosi and Senate Majority Leader Chuck Schumer on Capitol Hill, June 23.

Speaker of the House Nancy Pelosi and Senate Majority Leader Chuck Schumer on Capitol Hill, June 23.

Photo: Stefani Reynolds/Bloomberg News

‘There ain’t gonna be no bipartisan bill unless we’re going to have a reconciliation bill,” Speaker Nancy Pelosi said recently. Translation: Democrats won’t reach across party lines to pass infrastructure legislation unless they pass another spending bill with no Republican support.

I worked closely with Mrs. Pelosi and Senate Majority Leader Chuck Schumer for decades. They’re both great people and skilled legislative tacticians, and they apparently think this strategy is the only way to hold their fragile majorities together and give all Democrats at least some of what they want.

I hope they rethink their strategy. President Biden has agreed to an infrastructure proposal with a bipartisan Senate group and the House Problem Solvers Caucus. Linking it to a separate multitrillion-dollar partisan reconciliation bill would likely end with passage of neither. The American people wouldn’t soon forgive this failure, and they’d blame Mr. Biden and Democrats because we’re in the majority.

That risk became clearer last week when Mr. Biden went to Wisconsin to advocate for the bipartisan agreement, which would be the largest federal infrastructure investment since the creation of the Interstate Highway System 65 years ago. The president said the plan would create millions of good jobs and ensure America can compete with China. It would replace 100% of the lead water pipes that go into 10 million homes and 400,000 school across America, repair roads and bridges, upgrade the power grid, close the digital divide, make U.S. coastlines more resilient against climate change, and entail the largest investment in public transit in American history.

In other words, the president’s essential message in Wisconsin was that this is a historic plan every American should be very excited about, while the message from Mrs. Pelosi and Mr. Schumer in Washington is that we can’t have this infrastructure plan until Congress is done debating and voting for a separate, controversial, costly bill that may or may not pass months from now.

This is the kind of political gamesmanship that makes Americans cynical about our government and the people in it.

A few weeks ago—when White House talks with Republican Sen. Shelly Moore Capito collapsed—an infrastructure deal seemed dead. But then it was revived by the bipartisan G-10 (which eventually became the G-21) Senate group and the House Problem Solvers Caucus, each of which released similar bipartisan infrastructure plans. They then began negotiations with Mr. Biden that produced the bipartisan agreement.

The president said in Wisconsin that when he was inaugurated he “pledged to put my whole soul into bringing America together,” and this deal could prove once again there’s nothing we cannot do “if we . . . come together as a nation, Democrats and Republicans.”

The president is right and Mrs. Pelosi and Mr. Schumer are wrong. They are taking on massive risks—for Democrats but more importantly for the country—by refusing to accept a win that in almost any other era would be rightly seen as a defining achievement.

As this summer drags on, the momentum behind the bipartisan infrastructure deal may ebb. Minority Leaders Mitch McConnell and Kevin McCarthy, with an eye on the 2022 midterms, may start leaning on Republican senators and House members to back away from the bipartisan deal to deprive the president and Democrats of a great achievement. Any number of unexpected events—a Covid resurgence, an economic shock, a foreign-policy crisis—could stall negotiations.

If it all falls apart, Americans will be fuming and they would be justified in their anger. They won’t understand or accept why leaders in Washington couldn’t say yes to a deal protecting their kids from lead-tainted water, making bridges and highways safer, improving mass transit, growing the economy and creating jobs.

In Wisconsin, as Mr. Biden touted this bipartisan infrastructure plan, he promised to “fight for more” of his economic agenda including the child-care, educational, climate and other provisions Mrs. Pelosi and Mr. Schumer want to put in a reconciliation bill.

The president should keep fighting for these priorities. But in the meantime, the bipartisan infrastructure plan should move forward in Congress without delay or conditions. I hope Mrs. Pelosi and Mr. Schumer will come to this conclusion on their own. But if not, the president should personally request as the leader of the Democratic Party that its leaders in Congress support the bipartisan agreement and unlink it from other proposals.

Last week the president’s press secretary said the White House position is that it’s up to leaders in Congress “to determine the sequencing of the legislation.” That’s not good enough.

The president said in Wisconsin that this bipartisan infrastructure deal is historic. It is, and there is only one message he should send to Congress and the country: Let’s take the win for America. Let’s pass a bipartisan infrastructure bill now.

Mr. Lieberman, a Democrat, served as a U.S. senator from Connecticut, 1989-2013. He is a national co-chairman of No Labels.