Answer: Because it might pass — and this tells you everything you need to know about Washington DC. When Sen. Chris Murphy (D-CT) first proposed the Fix-NICS act last November, he had four members of each party as sponsors, calling it “the most important piece of bipartisan guns legislation since Manchin-Toomey.” The bill would plug the gaps in reporting by federal agencies to the background-check system, failings that contributed to the fatal church shooting that month in Sutherland Springs, Texas.

Now, though, Democrats have spent their first days back from recess rejecting Fix-NICS, and even Murphy doesn’t want a stand-alone vote for his “most important” bill. Why? Amber Phillips explains at The Washington Post:

It’s not that Democrats don’t want to patch up what both sides say are obvious holes in the background-check system; it’s that they think this is a small step to reinforce an existing law rather than expand it. And if they support it, that might be the end of gun control reforms in this Congress, since Republicans will be reluctant to act on much else. This leaves Democrats toying with opposing the one gun-control bill that has a realistic shot of passing Congress right now, one championed by their most vocal gun-control advocate, Sen. Chris Murphy (D-Conn.). It’s a weird look, for sure. Murphy doesn’t want his own bill brought up for a vote without a guarantee from Republicans to allow votes on other Democratic priorities, like universal background checks. “If we were only to debate the Fix NICS Act,” Murphy told reporters Tuesday, “we would be slamming the door in the face of all these kids who are demanding change.” That’s a sharp turn from what Murphy said in November, calling his bill the most important piece of bipartisan gun-control legislation since the Senate voted on (and didn’t pass) a universal background check proposal after the Sandy Hook shooting in Newtown, Conn.

If it comes to the floor, Fix-NICS would almost certainly pass for two reasons. One: It addresses an actual problem that actually contributed to a mass shooting. The Pentagon revealed after the Sutherland Springs shooting that the perpetrator — who was killed by an armed civilian responding to the massacre — had been convicted of a crime that would have disqualified him from owning a weapon. It also turns out that the same man had been named as a sexual assailant, but that the local law enforcement agency didn’t pursue the case vigorously enough to flag him in the system.

Two, and more importantly: Fix-NICS doesn’t intrude on the right to bear arms. And that’s what Democrats really want to get out of this particular political moment, as well as a wedge issue for the midterms. And guess who’s organizing that effort?

For years, Democrats have struggled to balance calls from the party’s base to push for stricter gun-control laws with electoral realities that see the party struggling to maintain support in rural areas of the country, where support for gun rights is stronger — and where groups such as the National Rifle Association often succeed in attacking Democratic candidates. But the recent shooting at a high school in Parkland, Fla., has exposed fissures in the GOP ranks, as several House and Senate Republicans are pushing to strengthen the national criminal background check system, supporting proposals to expand funding for mental health programs and even advocating for a ban on certain assault-style weapons. “A lot of us have a feeling that 2018 is going to be the first year in which this issue is a true liability to Republicans who refuse to break from the NRA at all,” said Sen. Chris Murphy (D-Conn.), who organized the meeting. “We also want to make sure that all of these new entrants into the issue stick with us into the elections. I’ve never had a meeting like this before with that many members of Congress and every anti-gun-violence group.”

Chris Murphy’s a busy guy, eh? In other words, Democrats don’t want to fix anything, not even with their own solutions to real issues. They want to posture for the upcoming elections and exploit the moment for maximum impact.

For those who wonder why nothing ever gets done in Washington, this provides an object lesson.