If the GOP presidential primary came down to a fight between Sens. Rand Paul and Marco Rubio, it would resemble a neighborhood brawl. Literally.

Their Washington campaign operations are housed on the same quiet, tree-lined Capitol Hill block. They can’t quite peer into each other’s windows, but we’re told the staffers recognize each other and regularly pass on the streets with a Jets-Sharks staredown.

One time, Paul’s mail was even delivered to Rubio’s address, and an intern had to awkwardly walk down the street to deliver it. (How neighborly.)

As we reported this week, Paul is the only presidential hopeful to officially list a D.C. address for his campaign. Rubio listed on his Federal Election Commission form that his headquarters is based in Miami.

But in fact, Rubio’s team is working out of a house on the 500 block of C St NE. (Not to be confused with the famous C Street in Southeast Washington where Christian conservative lawmakers lived together in a rowhouse.)

How can we know for sure? Because we visited.

Rubio and his top advisers weren’t inside because they were off doing debate prep (must be feeling confident about those poll numbers.) We only got as far as the front entrance, but we got to see the Rubio-branded cornhole game sitting unused in the corner.

Several doors down, separated by the American Foreign Policy Council (insert joke about their opposing views on that topic here), there’s the rowhouse where Paul’s presidential campaign is based on C St.

The inside smelled like fresh paint, and a poster-sized red silhouette of Paul’s head hung on the wall. There was another poster with his slogan “Defeat the Washington Machine” — from the belly of the beast! (We added that last part.) From the kitchen blared Taylor Swift’s “Bad Blood.”

We didn’t get past the entrance there, either. We asked for a tour, but were told the staffers were a little busy right then.

That’s okay. We’re just hoping for an invite to the block party.