Israel argued that "no one election creates a narrative for the next" and that "every election is an isolated moment in time and so is this one," but said the one lesson that could be derived from the Wisconsin results, in which Gov. Scott Walker (R) and his allies outspent Democrats by a wide margin, was that liberal groups needed to step up.

"Elections do give you a dry run for subsequent contests, and the lesson from this dry run is when you get outspent eight to one it's hard to compensate for that," he said.

Walker outspent Milwaukee Mayor Tom Barrett (D) by that margin, although total spending was more like two to one in favor of the GOP.

Another House Democrat said the lopsided spending was "frightening" for his and other Democrats' chances in the fall.

"These races are being bought and sold," said Rep. Mark Critz (D-Pa.), who faces a tough reelection fight in a Republican-leaning district outside of Pittsburgh. "We can only do so much with on the ground work. It's the money that's controlling it. It's frightening."

Critz, who with union help narrowly beat Rep. Jason Altmire (D-Pa.) in a primary earlier this year, said if he and his allies can't keep up with the spending it will be very difficult for him to survive his reelection battle.

"Two years ago we had a ground game that was second to none. In the primary we had a very good ground game and in the fall we'll have another ground game that's second to none. But if you're outspent two, three, four, five to one it's hard to overcome," he said. "You can only communicate directly with so many people in a cycle. It's very frightening."

While Wisconsin was the focus of the political world, California also held a bevy of primaries on Tuesday — and the results weren't great for Democrats, who hope to pick up at least two to four seats in the state.

One top recruit, Redlands Mayor Pete Aguilar (D), failed to get into the second round of the top-two all-party primary in a Democratic-leaning seat outside of Los Angeles, and another preferred candidate, Blong Xiong, lost to another Democrat in a competitive seat.

"We got everything we wanted but there's no question that the Aguilar dynamic was unexpected," Israel said. "They've had their setbacks. This was a setback for us. We're going to have to make it up elsewhere."

The DCCC chairman said he was "comfortable" with John Hernandez (D), who edged Xiong, and touted Julia BrownleyJulia Andrews BrownleyWorst engineering failure in U.S. history made us safer GOP leaders prevent votes to ban federal spending at Trump businesses Dem whip asks Ryan to allow floor votes on DACA this week MORE, José Hernandez and Scott Peters as three Democrats who could win tough seats for the party. But he dodged when asked about his earlier prediction of two to four seats in the state.

"Was the result with Aguilar disappointing and even frustrating? Yes. Does it make the difference between the majority and minority in November? No," he said, laughing when The Hill said that it would if there were only one seat dividing the parties.

"I don't think anyone who thinks one seat will swing it, it'll be a little under or a little over," he said.

—This post was updated at 5:35 p.m.