During. Sen. Chris Murphy's (D-Conn.) nearly 15-hour filibuster on gun control, exactly two Republican senators came to the floor to talk about it. One, Sen. Ben Sasse (Neb.), came to oppose new gun-control laws. The second was Sen. Patrick J. Toomey (Pa.), a man who in recent years has become the face of moderation for Republicans on new gun laws.

"I think everybody ought to be in agreement in principle," he said on the Senate floor Wednesday. "We don't want terrorists to be able to walk into a gun store and buy a gun, and we don't want an innocent, law-abiding citizen to be denied his Second Amendment rights because he's wrongly on the list with a bunch of terrorists."

If Toomey's name sounds familiar in the context of gun control, that's because it is. We'll get to his history in a minute, but the latest is that after the shooting at an Orlando nightclub, he's working with former New York mayor Michael R. Bloomberg's gun-control group, Everytown for Gun Safety, on legislation to prevent people on the FBI's various terrorist watch lists from purchasing guns. Having a Republican on their side gives gun-control supporters hope that finally, after this massacre, they'll be able to notch the legislative victory that has long eluded them.

As we said, this isn't the first time Toomey has crossed the party picket line on guns. So what is it about this guy that makes him willing to do so on one of the most politicized issues of all — one most Republican members of Congress won't touch? We have a few ideas — and you probably won't be surprised to hear that most of them involve politics.

He's done this before

As far back as his time in the House of Representatives — a stretch that lasted from 1998 to 2004 — Toomey is on record as supporting universal background checks, says his staff.

He'd get a chance to demonstrate his commitment to that about a year after joining the Senate. After the 2012 Sandy Hook massacre, Toomey agreed to partner with Sen. Joe Manchin III, a moderate Democrat from West Virginia, on legislation to expand federal background checks to gun purchases online and at gun shows. Politifact Pennsylvania reports that, at the time, Toomey was getting pressure from a gun-control group to support the legislation (as were a lot of Republican senators).

The Senate, then controlled by Democrats, voted on what became known as the "Manchin-Toomey" amendment four months after the tragedy. It came up five votes shy of the key 60-vote threshold, with four Democrats opposing it and four Republicans in favor. President Obama called the day one of his most shameful in public office.

In a statement, Toomey said he was disappointed but also that "it's time to move on."

He represents a blue-leaning state

The definition of a senator's job is to represent the state that elected you. And Pennsylvania is a quintessential blue-leaning, competitive state. It has voted for the Democratic candidate for president in every election since 1992. But Pennsylvania is also slowly turning red, argues David Wasserman with FiveThirtyEight, as the western, rural, older and whiter parts of the state start to resemble conservative Appalachia in their voting patterns, rather than suburban Philadelphia.

To wit, the nonprofit gun-control group Law Center to Prevent Gun Violence ranked Pennsylvania as middle of the road when it comes to gun-control laws — not the strictest (it doesn't have universal background checks) but not the most lax, either (it has a database of handgun sales).

Toomey was once head of the conservative Club for Growth, which targeted GOP incumbents from the right in primaries. He himself was also one of those more-conservative primary challengers, nearly upending then-GOP Sen. Arlen Specter (Pa.) in 2004 and then pushing Specter into the Democratic Party when Toomey ran again in 2010 (and won). But representing a state that leans slightly to the left means Toomey has needed to bolster his moderate bona fides; this was a good way to do it.

Four numbers: 2016

We're not implying that everything a politician does is aimed at getting reelected. But it's safe to say that when you're in a race as close as Toomey's is shaping up to be, supporting policies that are popular with a wider audience is a calculation you have to make.

Toomey is running for reelection as a Republican in state that tends to lean Democratic in a presidential year. His challenger is Katie McGinty, the former chief of staff to Pennsylvania's Democratic governor, who is aiming to be the only woman in the state's 20-person congressional delegation. Polls suggest the race is going to be close, and Democrats are counting on Toomey's seat being one of the four or five that they need to retake the Senate.

Most nonpartisan political analysts say this race is a pure tossup. We agree and have it fourth out of 10 in our top Senate races of 2016.

Back to what this means for the gun debate: A day after Orlando, McGinty tried to cast Toomey as a paper-thin supporter of gun control. "He lent his name to a bill, did little or nothing three years ago to try to get it passed, [and] since then has done absolutely nothing other than disavow any attempt to move on the legislation," she told the Philadelphia Inquirer's Jonathan Tamari.

It's a claim Politifact Pennsylvania rated "mostly false," but the two candidates' back-and-forth on guns is definitely attracting a lot of attention in the local media. That's not necessarily good news for Toomey.

But now, he's making headlines of his own, specifically that he's working with a gun-control group on legislation that Senate Democrats just spent nearly 15 hours filibustering to get a vote on. (The details and which party will support what are another matter, but that's for a different blog post.)

Two more words: Donald Trump

If there were ever a year when vulnerable Republicans needed to demonstrate to voters their independence, 2016 would be it. And that's because the candidate at the top of their ticket is hugely unpopular with precisely the kinds of voters that people such as Toomey want to appeal to: women, millennials and minorities.

As sure as the sun rises, Democrats are going to spend the next five months trying to convince voters Toomey that is one and the same with Trump. Trump's presumptive nomination puts an increased premium on Toomey doing something big to distance himself from his party on a timely issue such as guns. And given that he's secured the GOP nomination, Toomey has more latitude to tack to the middle.

Any way Toomey can show he's not a reflexive Republican is probably a good thing. And if it's on a major political issue in 2016 — guns — even better. That's why he's the rare Republican to really put himself out there on this.