"I expect personally that the rollout is going to be better in some states than others. That's natural, and we should learn from the states where the rollout is good and apply that wisdom to the states where it's not as good, where it hasn't been as good," he told reporters during a Wednesday meeting. "I can tell you from the perspective of our state it's nowhere near the train wreck, it's not recognizable as a  train wreck that these guys have made it out to be on the floor of the Senate. I don't anticipate the rollout of the Affordable Care Act is going to be material in this election in 2014, except that it may be very well to the good."

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 MoranGerald (Jerry) MoranOvernight Cybersecurity: Kushner was contacted about WikiLeaks before election | Tech experts blast Trump's 'extreme vetting' plan | Senate passes defense bill with measure to modernize feds' IT Ensuring that defense agencies will have access to a community of entrepreneurs and innovators Provision to modernize federal IT in compromise defense bill MORE (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.