Two of the biggest unions in the federal workforce — the American Federation of Government Employees and the National Air Traffic Controllers Association — are demanding that Democrats reopen the government now.

It’s not because they’ve turned MAGA or suddenly embraced the GOP budget: both unions are as progressive as ever. It’s because their members are working without pay. And the plight of these workers shows just how difficult it is for Democrats to wring concessions through shutdown tactics.

Because it’s illegal for federal workers to strike, these employees don’t have much choice. They are subject to what could be called an employer “lock-in”, where they are expected to work to maintain their employment status, their seniority, and whatever benefits they may have accrued. But so long as the shutdown continues, they will not be paid. This means that the people directing planes into runways are working six days a week for free. The army nurses caring for service members have gone unpaid for a month. The food inspectors, security forces, and all manner of safety and regulatory employees have spent the past four weeks without pay. It’s immensely unfair, unsafe, and for the unions representing them, it’s humiliating.

Worse than this, the shutdown puts their employer, the federal government, and their boss, Donald Trump, at a tremendous advantage. The longer the government can keep them from being paid, the higher the chance these workers resign to find work elsewhere. And shrinking the government workforce has long been one of Trump’s goals. In some sense, he can win through attrition what he planned to force through legislation.

Politically, liberals have sorted themselves into groups in support of or in opposition to the shutdown based on whether the move hurts Trump in the polls. This seems like a mistake. It may be that Americans blame the President for the shutdown, but it is unlikely that this is enough to persuade them to vote differently. What’s more, the Democrats have made a mess of capitalizing on the shutdown: right now, it’s difficult for the average person to even understand what it is the Democrats are aiming for in their negotiations.

Democratic leaders think the shutdown will demonstrate that the GOP can’t govern. The trouble is that pointing out how dysfunctional and ultimately unworkable government can be is a major ideological tenet of the Republican Party. To say that the government is failing is to affirm the party’s program. Nor does the GOP feel any obligation to federal government employees, who are a constant object of scorn by the Right.

It’s true that many of the benefits which have been turned off as a result of the shutdown overwhelmingly affect Republican-dominated regions. This may yet aid Democrats as voters’ hardships are turned on Trump’s recklessness. But this is far from a foregone conclusion — it is just as likely that these conservative voters blame Democrats for taking a stand.

This isn’t to say that Democrats are stupid for trying. Instead, it’s to recognize that there are times when it seems your opposition holds all the cards.