During President Franklin D. Roosevelt's administration, Zelizer recalls, the unified Congress forced the president to negotiate constantly between the Northern Democrats and the Southern Democrats.
"FDR managed to find bills that both sides could support, but often ended up watering down legislation because he didn't want to offend the Southerners," said Zelizer.
Even though all liberal legislation won't be easily agreed upon, there are some measures that will likely benefit from the single-party rule in Congress.
Mathias says legislation regarding regulation of the financial services industry and the taxation of carried interest are two issues that are likely to benefit from Democratic majority rule.
Mathias said that issues like energy policy and agriculture policy – which is much more regional -- probably won't be helped that much by the Democratic majority.
"Democrats are naturally ideological, and as a party are interested in inclusion and broadening the participants in the democracy," said Mathias. "So they're bringing in outsider candidates more easily than the Republicans, and as a result they get a lot of people with a lot of different points of view."
Some of the newly elected senators, such as Democrat Kay Hagan in North Carolina, might have to answer to their traditionally more conservative constituencies, making it difficult to consistently vote with their parties, said Mathias.
"I don't think people will see a lock-step liberal agenda that everyone is worried about," said Mathias. "[These senators] are still going to have to respond to constituents who are very different from them -- and often times a lot more conservative."
So what will a unified Congress mean for a President Obama?
Some aspects could be worse than had a divided government, according to Mathias, who said Democratic senators may come to expect Obama's support.
"You could make the argument that it could make it more difficult to reach an agreement because they're all the same party," she said. "The senators may expect Obama to always agree with them because he's also a Democrat."
But even with those headaches, the sweeping victory on Election Day means that Obama will enter office with a stacked Congress and every opportunity to push through many of his legislative goals.
Boston University's Kriner reminds that even though Democrats will be celebrating their victory in the days to come, the win comes with a lot of responsibility.
"There's no doubt that this win will be a huge ego boost for the party and will bring them back to the glory days," said Kriner. "The GOP will have to regroup and decide what they'll do the next time around."
"But with the opportunity comes danger -- the danger of not living up to public expectations is a real problem for the Democrats," he said.
With the bad economy and the financial crisis coupled with two wars, the Democrats don't have an easy job ahead of them.
"They have a horrible hand dealt to them and it's not going to be easy," said Kriner.
"The public has said they want unified change and will now say to Congress, 'OK, we've given you the keys,'" said Kriner. "And if the Democratically-ruled Congress doesn't produce, they'll face an angry electorate in two years."