Trone's Senate campaign left Maryland's 6th District in the western part of the state with no incumbent. On the Democratic side, former Commerce Department official April McClain Delaney and state Del. Joe Vogel look like the front-runners for the Democratic nod. McClain Delaney's name may sound familiar: Her husband, former Rep. John Delaney, represented the old version of this district for three terms. Running on her connections to Biden and work to keep kids safe online, McClain Delaney has self-funded a bit more than half of the $1.9 million she's raised, and she has some high-profile endorsements, including from The Washington Post.

Meanwhile, Vogel is a 27-year-old Latino legislator who is also gay and Jewish. He has raised $687,000 and enjoys endorsements from the powerful state teachers union and the LGBTQ+ Victory Fund. He's also received nearly $400,000 in outside spending help from the pro-LGBTQ Equality PAC, according to OpenSecrets. Competing surveys show a close race: A late April Public Policy Polling survey for McClain Delaney's campaign gave her a 37-percent-to-24-percent lead.

—Geoffrey Skelley, 538

As Geoffrey alluded to, the unexpected entrance of AIPAC's super PAC, United Democracy Project, into the Democratic primary in Maryland's 3rd District is one of the biggest stories in Maryland politics right now. The pro-Israel group arguably upended the race with its significant spending (More than $4.2 million as of Friday) on behalf of Elfreth, elevating her from a pack of a half-dozen current and former elected officials — three state delegates, another state senator and a prominent labor attorney — to be the top challenger against Dunn.

UDP has lapped the entire field in spending on TV, allowing Elfreth to go punch-for-punch against Dunn even though he has dominated fundraising (although, after UDP entered the race, Elfreth's own fundraising picked up too). Lam had been keeping pace with Elfreth in fundraising until UDP got involved, but he simply hasn't been able to compete in the ad wars and now lags in polling.

What makes UDP's involvement particularly striking is that neither Elfreth nor Dunn are focused on Israel issues or appear to have much daylight between them on the topic. Dunn even produced a white paper arguing for unconditional support for Israel and its right to defend itself. That's a difference from some other races UDP has gotten into, including a very expensive primary in Maryland's 4th District in 2022 and the recent Republican primary in Indiana's 8th District, both of which featured candidates with records that frustrated the pro-Israel group.

UDP's stated reason for spending here, according to the Huffington Post, was actually to stop John Morse, a labor attorney who has been critical of the Israeli government since Oct. 7. But that explanation has never really held water among Maryland political observers for the simple reason that, despite an endorsement from Sen. Bernie Sanders and some progressive backing, Morse has never been a factor in the race. He's raised just $123,000 — a fraction of Elfreth's haul, let alone Dunn's — and has never polled higher than 3 percent. If that's the real reason, it's not a wildly compelling one.

Some Dunn allies believe the real reason is donor maintenance on UDP's part — that one or a handful of the group's donors have beef with Dunn unrelated to Israel and are using UDP as a conduit to block him. It's speculation, but it's as good a theory as any that UDP has offered itself, especially since the group continued to pour money into the district long after it was clear Morse was destined to be an also-ran.

—Jacob Rubashkin, Inside Elections

Running between Washington, D.C., and Baltimore, the solidly blue 3rd District sits open following the retirement of Democratic Rep. John Sarbanes. A deluge of money has flooded the contest, mainly in support of former Capitol Hill police officer Harry Dunn and state Sen. Sarah Elfreth, although state Sen. Clarence Lam may have an outside shot at winning.

Dunn became prominent after he testified before Congress in July 2021 about defending the Capitol against insurrectionists on Jan. 6, 2021, later receiving a Presidential Citizens Medal for his service. Notably, Dunn's campaign launch video featured him speaking to camera while walking through a recreation of the events of Jan. 6. His announcement precipitated a money monsoon: Dunn raised more without self-funding in the first quarter of 2024 ($3.8 million) than any other non-incumbent House candidate. Overall, he's raised $4.6 million, which has allowed him to run ads emphasizing his background, an endorsement from Rep. Nancy Pelosi and his goal to protect democracy. Dunn has loose ties to the 3rd District area, however, as he lives in Montgomery County closer to the nation's capital.

By comparison, Elfreth likely started out better-known, as around 60 percent of her Annapolis-based state Senate seat lies in the 3rd District, according to Daily Kos Elections. She's raised about $1.5 million, but Elfreth has also received $4.2 million in outside spending support from United Democracy Project, the bipartisan American Israel Public Affairs Committee's super PAC. Despite AIPAC's pro-Israel policy focus, UDP's ads have emphasized Elfreth's effectiveness as a legislator and work to protect abortion rights. For his part, Lam has raised $736,000, but he sat in third with 8 percent in a late April survey for Dunn's campaign conducted by Upswing Research, while Dunn narrowly led Elfreth 22 percent to 18 percent.

—Geoffrey Skelley, 538

The retirement of Democratic Rep. Dutch Ruppersberger has left the solidly blue 2nd District open, making the seat's Democratic primary the main event. In that race, Baltimore County Executive John "Johnny O" Olszewski looks favored against state Del. Harry Bhandari, thanks in part to a sizable fundraising edge: Olszewski has brought in $837,000 to Bhandari's $181,000. And Baltimore County as a whole makes up about three-fourths of the seat's population, according to Daily Kos Elections, making Olszewski a familiar face to 2nd District voters.

—Geoffrey Skelley, 538