A long-time Democratic congressman in a traditionally blue state, Cardin held off tough primary challenges and seemed headed for a big win — until his opponent unleashed "The Puppy."
In a commercial, Republican candidate Michael Steele warned voters to ignore attack ads on his character, saying "For the record, I love puppies."
But Cardin lashed back — charging Steele with using the cute canine to conceal his identity and his ties to an unpopular president.
"The dog's not even his!" a Cardin commercial says.
Lt. Gov. Steele is the first African American to win state-wide office in Maryland — from either party.
He's jabbed at Democrats for not promoting more black candidates to top spots on their tickets, saying "I don't see us represented."
With polls showing the race tightening — Democrats brought out their own big dog — Illinois Senator Barack Obama — to shore up support.
Obama urged black voters not to use race as a litmus test.
"Maryland, I think everybody has to understand that you don't vote for somebody because of what they look like. You vote for what they stand for," he said to a cheering crowd.
Still, even some Cardin supporters admit Steele has a point. Many blacks believe the Democratic Party has taken African Americans for granted.
This week, key black Democratic politicians and pastors broke ranks to sign on with Steele.
Steele's surprising success is a warning to Democrats, says University of Maryland Political scientist Ron Walters.
"That's caused a tremendous explosion," he said. "And what it's done is really is a shot across the bow of the party, and started thinking maybe there is a move toward him."
Democrats on the national level are keeping an eye on the Maryland senate race and here's why: The state votes 2:1 for Democrats, and 1 in 5 Maryland Democrats are African American.
The bottom line of that is that Cardin has got to hang onto Black democrats to win. If he doesn't, it's going to be a blow not only to him but to his party as well.
Analysts believe that if Steele gets 30 percent of the black Democratic vote, he'll win the seat. That could be a stretch. But analysts say that anything over 20 percent would be considered a win for Republicans, indicating that they are able to make significant inroads with African American voters — even in a very blue state — if they have the right candidate.