Answer: I'm not surprised by Elfreth winning
Dunn's fundraising and national profile always made him look like the frontrunner in Maryland's 3rd, but Elfreth ran strong from the beginning, and the scant polling of the race we had showed her even with Dunn or ahead of him, before, during and after the UDP spending push (which, as Geoff noted, allowed the pro-Elfreth voice to be louder on TV than the pro-Dunn voice). And Elfreth's team was confident heading into today. I spoke with one of her allies this morning who was blunt in their assessment of the state of the race: "Elfreth will win it. She had TV plus organizing." Sometimes, it's that simple!
—Jacob Rubashkin, Inside Elections