Let’s see... a guy who’s ran for Senate three times and lost by 24 points (62% - 38% to Sarbanes in 1988), 42 points (71% - 29% to Mikulski in 1992), and 46 points (73% - 27% to Obama in 2004).
While he’s a great guy, he’s unelectable.
To be fair, I would not count the MD elections. Due to of a quirk of geography, MD contains both a densly populated urban core (Baltimore) and a rich, liberal suburb of DC (Montgomery County). These two jurisdictions dominate the state electorally. For a Republican to be elected at the state level is a (very uncommon) abberation.