Why it matters: If the White House acts on that legal analysis, it would dramatically escalate President Trump's pressure on Senate Democrats to end the week-old shutdown by denying back pay to as many as 750,000 federal workers after the shutdown.

I'm not sure it would. In the past, federal workers were always paid after the government opened up. If they aren't paid this time when the GOP holds both the Executive and the Legislative branches, it would be silly to claim the Democrats would have the power to withhold payment.

Why would that stop them from saying so?

It doesn't stop them saying it. It stops it from being credible. Ever other GOP and Democratic President has always paid, even in trump's first term during that shutdown. Now suddenly they can't? If you mess with a worker's pay you have highly reactive results.

These people don't care about credibility.

These people DO care about their paycheck, thats the difference here.