Bennet also ripped Republicans who have discussed using the looming debate over raising the debt ceiling to defund ObamaCare.
"It is perplexing to watch these guys here obsess over defunding ObamaCare in the debt ceiling conversation. It doesn't make any sense to people at home," he said.
Democrats are defending seven seats in red states, including open seats in Montana, West Virginia and South Dakota that look like likely Republican pickups because they've so far struggled with recruiting. Bennet admitted the party had yet to land strong candidates in those states, but argued the year was still early — and pointed to similar GOP recruiting struggles in Michigan and Iowa. Bennett said he was "optimistic" Democrats would retain Senate control.
"Both sides have work to do to make their respective races competitive," he said. "Republicans have not missed an opportunity to miss an opportunity…. Republicans have failed to put any blue or purple state into play."
The National Republican Senatorial Committee argued it has a good shot at winning back control.
"There's a lot of hard work to be done, but we feel very comfortable about the progression of the map in our favor and the quality of Republican candidates expressing an interest in running in key states," NRSC Chairman Jerry Moran (R-Kansas) told The Hill in a statement. "The majority is in play, which is a good thing for Americans who seek a functional Senate that will focus on the issues that matter most to middle-class families and workers."
Bennet outlined th "Big six" states that are likely to determine Senate control: Alaska, Arkansas, Louisiana, North Carolina, Kentucky and Georgia. Republicans need to win five of those six states and defeat four Democratic incumbents to win back control.
He compared the gelling conventional wisdom to the same time two years ago, when many assumed Democrats would lose control of the Senate. Instead they gained a net of two seats.