Senate Majority Leader Harry Reid (D-Nev.) predicted Democrats would retain control of the Senate in November "unless something unexpected happens."
Speaking to a Jefferson-Jackson brunch in his home state on Sunday, Reid urged supporters to stay motivated a little less than 80 days before the election.
Democrats are facing a tough midterm landscape and are defending 21 seats, a number of which are in Republican-leaning states. Republicans need to net six seats to win control of the upper chamber, and are heavily favored in South Dakota, West Virginia and Montana.
Republicans also have high hopes of winning an open seat in Iowa, and of knocking off Democratic incumbents in Louisiana, Arkansas, Alaska and North Carolina. Democrats think they have a chance of defeating Senate GOP Leader Mitch McConnell in Kentucky, and of winning Georgia's open Senate seat.
Reid expressed concern about the race in South Dakota, where Sen. Tim Johnson (D-S.D.) is retiring. He also commented on the millions of dollars being spent by the Koch brothers against Democratic Sen. Kay Hagan in North Carolina.
Billionaires Charles and David Koch have been a favorite punching bag of Reid this election cycle. He used his speech to again attack them for their involvement in national and state races.
"They think they have enough money to buy America," Reid said. "Not only with the U.S. Senate, not only with the House of Representatives but with the constitutional offices as well. They are even involved with the state senate races here as well."