As the showdown over continuing to fund the government intensified today, Dem Senator Mary Landrieu made a startling confession. Democrats “grew a backbone,” she said. “We normally cave.”

That’s very true. But not this time. And their unwillingness to “cave” so far speaks to their new reading of the political landscape, which they think has shifted in their favor after the debt ceiling fight.

In the Senate today, Dems stood firm in their opposition to funding disaster relief with offsets elsewhere, as Republicans want. Senate Democrats voted down a House GOP-authored measure to temporarily fund the government, intensifying the impasse over the disaster relief funds, even as FEMA is set to run out of money next week.

At a presser after the vote, Dem leaders vowed they would not blink. Asked if there were any offsets Dems would accept, Harry Reid said: “No.” That seems like a pretty high stakes gamble. As Eric Cantor put it: “I guess Harry Reid will have to bear the burden of denying disaster victims the money they need.”

But Senate Dems don’t appear worried about bearing the blame in this standoff — they continue to insist they won’t budge, and continue to demand that the House drop its insistence on offsetting the funds. Their argument: Disaster victims need help, period, and they should get it with no political strings attached.

Dems could revert to type and "cave” at any moment. But why the current firm line? It goes to the heart of the Dems’ new calculus after getting shellacked so badly — and giving up so many concessions — in the debt ceiling fight.

My read: Dems think the debt ceiling battle has successfully established them as the reasonable party that’s seeking true balance on fiscal issues, having agreed to so many GOP demands on the spending cut front. Dems also believe the debt ceiling fight established public perceptions of the GOP’s pursuit of endless spending cuts as being fundamentally ideological in nature, and not motivated by a desire to craft sensible policy. Dems also believe — or hope — this impression was solidified by the House GOP’s initial failure to pass a funding bill when conservatives decided it didn’t cut spending enough. The House GOP finally passed a bill after John Boehner strongly rebuked conservatives, telling them that if they didn’t get on board, he would have to move to the left to get Dem support, and Dems hope Boehner’s anger will be seen as a sign that he’s lost control of his caucus’s ideological wing.

“They were trolling for votes for maybe more than 24 hours, to try to get enough votes to satisfy the tea party,” Reid said at the presser today, describing why he thinks the House GOP is in a weak bargaining spot.

And so, Dems are acting as if they have the upper hand in this fight — even though Republicans are doing what they’ve customarily done, i.e., insist on ever more spending cuts and refuse to blink, even if the consequences could be dire. Do Dems really think the changed landscape means the GOP will ultimately have to blink? I don't know, but they’re sure acting like it. We’ll see if the Dem posture holds — or whether Landrieu’s diagnosis of the Dems’ tendency to “always cave” remains accurate.