Sen. Mitch McConnell's (R-Ky.) primary challenger is one of several conservative candidates running for Senate who have blasted the budget deal expected to come to a House vote as early as Thursday.
The criticism from conservative primary challengers could make it tougher for McConnell and other Senate and House Republicans to back the deal.
McConnell challenger Matt Bevin accused McConnell of being "missing in action" on the budget deal.
"Instead of leading, he is dodging a major issue while waiting to see which way the political winds are blowing," he said.
"It's high time we change Washington by changing the people we send there. We deserve better, and in 2014, we will go to the ballot box and demand better."
Mississippi state Sen. Chris McDaniel, who's challenging Sen. Thad Cochran (R-Miss.), called the deal "a complete abdication of Washington’s governing responsibility."
"Unfortunately, Republicans in Washington are just as much to blame as Democrats," he said. "After increasing spending for years, many Republican politicians are now acquiescing to Democratic demands to continue business as usual. I urge Sen. Cochran to reject this deal and insist on absolutely no spending increases."
Milton Wolf, running against Sen. Pat Roberts (R-Kans.), said the deal was "irresponsible" and asked why Roberts hadn't yet weighed in on it.
"It's time for Senator Roberts to put Kansans first and stand up to the out of control Washington spending. A Senator should have more than a vote. He should have a voice. Why is Senator Roberts silent on this deal and when will he start fighting for Kansans?”
Both candidates criticized the deal negotiated by Rep. Paul Ryan (R-Wis.) and Sen. Patty Murray (D-Wash.) for raising spending higher than the $967 billion ceiling set by sequestration.
The deal would replace $63 billion in sequester cuts with other savings, and includes an additional $22.5 billion reduction in the deficit.
It does so by raising Transportation Security Administration fees and making changes to federal worker retirement plans, among other things.
A number of conservative lawmakers, including Sens. Marco Rubio (R-Fla.) and Rand Paul (R-Ky.) — both considered likely presidential contenders — have also come out against the deal.
And conservative groups like the Club for Growth and Heritage Action have joined the chorus against the deal, designating it a key vote — a development that would make it tougher for Ryan to carry Republican support in the House.
Though McConnell, Cochran and Roberts are favored in their races, both are considered vulnerable in their primaries, and have taken steps to shore up support on their right flanks.
All three of their challengers have been endorsed by the Senate Conservatives Fund (SCF), a prominent national conservative group that engaged heavily in primaries last cycle. In an email to The Hill, SCF Executive Director Matt Hoskins called the deal "horrible" and placed the blame squarely on McConnell's shoulders.
"It increases spending, raises taxes, and funds Obamacare for two years. This is a direct result of Mitch McConnell's failed leadership. He made it clear that he won't fight the Democrats on spending and forced his party to surrender," Hoskins said.
"Conservatives in Congress want to fight for something better, but their leadership won't allow it. This deal makes one thing clear. The only way to save this country is to replace establishment Republicans with true conservatives in the mid-term elections starting with Mitch McConnell."
Bevin's challenge put McConnell in a tough spot on the last government funding deal, when he supported a conservative-led strategy to shut down the government to defund ObamaCare.
McConnell, known for his deal-making abilities, remained largely on the sidelines for much of the fight as the shutdown dragged out and hurt Republicans in the polls.
The Senate minority leader ultimately brokered a deal to end the shutdown but drew conservative fire for his role in the compromise.
--This piece was updated at 12:36 to reflect comment from Wolf.