Democrats are doing it again.

They’re forced to use conventional political tactics to battle the most unconventional president in history — repeating a scenario that keeps leading them to political disaster.

At first sight, in the third week of the government shutdown, things seem to be working out better than expected for the opposition party locked out of Washington power. They’ve made their key issue — looming health insurance premium hikes — a national story. They’ve opened divisions in the Republican Party. And contrary to stereotype, they didn’t immediately cave, showing supporters a backbone.

In classic shutdown politics, this might have laid a decisive trap for their Republican opponents, as the human cost of the showdown mounts to create a political imperative for the party in power to find an off-ramp.

But this is the nihilistic age of Trump.

The president doesn’t just move the goal posts; he rips up the entire pitch. So assumptions that governed previous shutdowns over 30 years of bitter partisanship in Washington may not apply.

The shutdown started three weeks ago when Senate Democrats refused to back a seven-week spending bill, using the end of government funding as leverage to try to force Republicans to extend expiring Affordable Care Act subsidies and to push for a rollback of Medicaid cuts contained in Trump’s big domestic agenda law.

R