Today Senate Democrats voted for the third time this year to prevent the defense appropriations bill from moving forward.

The Democrats did this for one simple reason: they want leverage to push their liberal priorities in all the other spending bills. In short, they are using military funding as a hostage.

Just last week, the Senate passed the Bipartisan Budget Act, a budget deal that raised the legal spending caps for both defense and non-defense discretionary spending. This deal, which was opposed by many Republicans, gave President Obama and Democrats in Congress 100 percent of the funding level they want for non-defense agencies, will cutting defense by $5 billion.

The Democrats argued, when they stopped this bill this summer, that they wouldn’t allow a defense bill to move forward until they got a budget deal that raised non-defense spending.

So, if there is a budget deal, why are Democrats holding the defense spending bill yet again?

It’s all about political leverage. Even though Republicans have majorities in the House and the Senate, Senate Democrats are willing to put military funding at risk in order to ensure that they have leverage over the other funding bills.

Senate Democrats are essentially betting that Senate Republicans care enough about the military to give up on some of their priorities in other areas. In this case, that might mean policy riders aimed at onerous red tape or efforts to defund Planned Parenthood.

Senate Democrats also want extra assurance that their liberal funding priorities will stay in the final bill, things like an extra $500 million for the Environmental Protection Agency and $6 billion more for the Department of Housing and Urban Development.

Interestingly, right after blocking the military funding bill the Senate began considering the military construction and Veterans Affairs funding bill and there are indications that Democrats might allow this bill to move forward.

The fact that Democrats would even consider blocking the VA spending bill is pretty amazing, but allowing it to move forward is a step in the right direction. Unfortunately, this only highlights their crass political move on the military funding bill. In essence, Senate Democrats are saying that they won’t use veterans for political leverage, but it is ok to use future-veterans—men and women in uniform today—for leverage.

This type of hypocrisy is not new in Washington.

Obama’s veto of a parallel defense bill is another recent example. A debate about the specifics of military funding is good and healthy, but using the military for political leverage needs to stop.