Speculation has been brewing that Rep. Joe Kennedy III would challenge Sen. Ed Markey in next year's primary. On Monday, Kennedyresponded to those whispers. He posted on Facebook and confirmed he's considering a Senate run, but cautioned he hasn't yet made his final decision. Almost an hour later, Kennedy filed a statement of organization with the Federal Election Commission to create a “Kennedy for Massachusetts” Senate campaign committee. WGBH Radio Political Reporter Adam Reilly spoke with WGBH’s Jeb Sharp about the implications of a possible run by Kennedy. This transcript has been edited for clarity.

Jeb Sharp: It’s hard not to pay attention when the Kennedy name pops up. How big a deal is this?

Adam Reilly: To me, it seems like yet another sign that he is in fact seriously thinking about running for Senate against a Democratic incumbent, if he hasn't already made up his mind.

I think it's worth pointing out there is a stage craft to this sort of thing. If he — and I don't have inside information that this is the case — but if he were locked in and firmly committed to a Senate run, he would still need to sort of engage in the public performance of grappling with it. You know, 'Is this tenable? Is this something that I want to do? Is this something that the people want me to do? I'm thinking it through.' It's almost bad form nowadays to say, 'Yeah, I'm actually going to take this on.' So again, I don't know if this is genuine or not, but it's what he has to do either way.

Sharp: Yeah, you make a good point. Any significance to the timing?

Reilly: Not as far as I can tell. One thing that forming this Senate committee will allow him to do is, if he gets a ton of money, then that becomes something that he can point to as a sign of strength. If he's trying to force Markey out of the race, then it becomes a data point that Sen. Markey has to ponder.

Sharp: So if he does indeed run against the incumbent, Sen. Ed Markey, what sort of a contest does that set up? Is there a stark choice here?

Reilly: What I'm most interested in here is that ideologically speaking, it's not like Joe Kennedy would be coming at Ed Markey from the left. Like, for example, Ayanna Pressley did with Mike Capuano. Although there, too, Capuano was progressive in many areas, but you had this stark difference in terms of demography, right? And Pressley was able to make the case that representation matters and that it was a good time to send an African-American woman to the Congress. Here you have two white men, one of whom comes from this long established political clan. So that makes it a little tougher, I think, for Joe Kennedy to position himself as an outsider.

What he might be able to do is position himself as a youthful alternative to Markey. That's a dynamic that we've seen playing out with increasing frequency in Massachusetts politics, going back to when Seth Moulton took on Rep. John Tierney. A lot of people thought, 'Wait, what the heck's going on here? You can't just run against an incumbent congressman.' And Seth Moulton did and he won.

Now we have this race, potentially. We have Alex Morse saying that he is going to take on Richard Neal, who's the chair of the House Ways and Means Committee. So all of a sudden, in the span of a few short years, it's become normal to have an incumbent who is a little on the older side face a challenge from someone who's young and ambitious.

Sharp: Well either way, it's gonna be fun to watch.

Reilly: It will be, if it happens.