Journal Editorial Report: How many Democrats share the Senator's doubts? Image: Al Drago/Bloomberg News The Wall Street Journal Interactive Edition

Democratic fault lines are becoming clearer following Sen. Joe Manchin’s op-ed in these pages last week calling for a “strategic pause” on his party’s multitrillion-dollar spending bill. Chuck Schumer and Bernie Sanders look ready to jam him anyway.

The West Virginian signaled that he won’t support the left’s $3.5 trillion in climate and entitlement spending, and he’s now getting more specific. Axios on Tuesday reported that Mr. Manchin told White House and Democratic leaders that he can’t support more than $1.5 trillion, and he has policy issues too. He wants to means-test key programs and has well-founded doubts about a new $400 billion entitlement for home care.

Mr. Schumer isn’t listening. “We’re moving full speed ahead” to “get something big done,” the Senate leader told reporters Wednesday, having instructed committee chairs to rush out language by Sept. 15. Mr. Sanders rejected changes to the timing or size of his budget. At the “very least” the bill must be $3.5 trillion, he said, since the figure was “already the result of a major, major compromise.” That must have been Bernie negotiating with himself down from his fantasy of $6 trillion.

Give Mr. Manchin credit for standing up to progressives who are heaping him with scorn. He knows a $3.5 trillion blowout is a political killer in a state that Donald Trump won by 39 points. His economic rationale is also solid. He says record spending is already contributing to inflation as the Federal Reserve accommodates it, and Washington needs fiscal space in case of an unforeseen crisis.

As the decisive vote in a 50-50 Senate, Mr. Manchin has the most leverage. One progressive counterpunch would be to start the entitlements small and means-test them to reduce their 10-year cost. The programs would invariably expand in the future. That may have to be the Sanders fallback, though it would still violate Mr. Manchin’s fiscal principles.

The White House also shrugged off Mr. Manchin’s concerns, with Chief of Staff Ron Klain telling CNN Sunday that the Senator is “very persuadable.” They’ll have to hope so. For now the Democratic plan seems to be to roll right over Mr. Manchin’s “pause” and dare him to say no.