Spending $3.5 trillion on a budget bill apparently doesn't satisfy the progressive imperative. Democrats control the 50-50 Senate thanks only to the vice president as tiebreaker, and they lack the votes to nuke the filibuster.

Nevertheless, they insist that their mammoth budget bill must also include big policy changes, even if it takes bending Senate rules beyond recognition. This month the Senate's parliamentarian heard arguments from both sides on how much a reconciliation bill can rewrite immigration law. Democrats want to give green cards to as many as eight million people.

Legalizing the so-called Dreamers who came here as children is a good idea on the merits, but is it a budget item? The obvious answer is no, and everybody knows it. Legalizing 8 million people would have budgetary effects, but revenues and outlays are clearly beside the point.

The House Education and Labor plan, meantime, would rewrite U.S. labor law to give unions a new advantage. "It shall be unlawful," one provision says, for an employer to "promise, threaten, or take any action" to "permanently replace an employee who participates in a strike." Another section would create civil penalties for "unfair labor practices," up to $100,000 a pop. Company directors and officers could be held personally liable if they so much as "established a policy that led to such a violation."

The House Energy and Commerce proposal would launch a Clean Electricity Performance Program. Starting in 2023, energy suppliers that increased their clean power by four percentage points a year would receive grants for a portion of that gain, based on a formula of $150 per megawatt-hour. Those that failed would owe "a payment" — is this a fine, or maybe it's a tax? — based on $40 per megawatt-hour. It reads like regulation by alternative means.

To qualify for passage under reconciliation, a provision is supposed to affect the budget in a way that's more than incidental. This is part of what's known as the Byrd rule. When the reconciliation process was set up in 1974, the temptation was to label everything budgetary.

In the 1980s, Sen. Robert Byrd moved to limit these abuses. The Byrd rule has been stretched since then, but it still imposes at least some discipline on reconciliation. In February, Sen. Bernie Sanders wanted to use the budget process to enact a nationwide $15 minimum wage. The parliamentarian, Elizabeth MacDonough, said this proposal was extraneous. Six years ago the same thing happened when Republicans wanted to ax ObamaCare's mandate to buy health insurance, so the GOP eventually settled for cutting the penalty to $0.

MacDonough hasn't said when she plans to rule on those 8 million green cards, but she's under enormous pressure to wave things past the Byrd rule. After she nixed Sanders's $15 minimum wage, some Democrats called for her to be ignored — or fired. Perhaps their strategy today is to blitz MacDonough with so many incidental provisions that some are bound to make it through.

Yet if immigration or labor law can be rewritten by reconciliation, then the Byrd rule will be as dead as the dodo, and don't expect Republicans to turn the other cheek. To quote GOP Senate leader Mitch McConnell's comment in 2013 about breaking the filibuster for judicial nominees, Democrats might regret this, and a lot sooner than they think.