Updated 8:14 p.m.

The Senate on Wednesday evening rejected a Republican measure that would limit the Environmental Protection Agency’s authority to regulate greenhouse gas emissions.

The measure, proposed by Senate Minority Leader Mitch McConnell (R-Ky.) and Sen. James Inhofe (R-Okla.) as an amendment to a small-business bill that the Senate has been working on since mid-March, failed Wednesday on a 50-to-50 vote. Sixty votes were necessary for passage.

Four Democrats – Sens. Joe Manchin (W.Va.), Ben Nelson (Neb.), Mary Landrieu (La.) and Mark Pryor (Ark.) – joined most Republicans in voting for the measure; one Republican, Sen. Susan Collins (Maine), joined Democrats in voting against it.

Ahead of the final vote on the Republican measure, the Senate also rejected three Democratic EPA-related amendments.

One, sponsored by Sen. Max Baucus (D-Mont.), would have provided exemptions for agriculture and smaller greenhouse gas emitters from the EPA’s permitting process; another, sponsored by Sen. Jay Rockefeller (D-W.Va.), would delay EPA rules for two years; and a third, sponsored by Sen. Debbie Stabenow (D-Mich.), would have delayed the rules for two years, exempted agriculture and provided a tax credit to clean energy technology manufacturers.

In remarks on the Senate floor Wednesday morning, McConnell criticized those measures as “sham amendments” designed to give Democrats political cover.

“Well, Republicans have a better idea — let’s try to make sure everybody is exempted” from the EPA regulations, McConnell said. “Let’s not pick winners and losers. Let’s let America’s small businesses and entrepreneurs compete and grow on a level playing field without any more burdensome government regulations, costs or red tape. The McConnell Amendment would do that.”

The House on Wednesday was also considering a measure sponsored by House Energy and Commerce Committee Chairman Fred Upton (R-Mich.) that would prevent the EPA from regulating greenhouse gas emissions under the Clean Air Act. Democrats proposed 12 amendments to the measure, only one of which was passed by the House on Wednesday. A vote on final passage of the measure is expected Thursday.

The amendment that passed, was sponsored by Rep. Jerry McNerney (D-Calif.), clarified that voluntary programs addressing climate change are exempted from the bill’s provisions.

The 11 amendments rejected Wednesday included one sponsored by Rep. Henry Waxman (D-Calif.) that would have added a section to the Upton bill stating that “Congress accepts the scientific findings of the Environmental Protection Agency that climate changes is occurring, is caused largely by human activities, and poses significant risks for public health and welfare.”

That amendment failed on a 184-to-240 vote; one Republican, Rep. Dave Reichert (Wash.), voted with most Democrats in favor of the measure, while three Democrats, Reps. Dan Boren (Okla.), Collin Peterson (Minn.) and Nick Rahall (W.Va.) joined most Republicans in voting “no.

.Earlier Wednesday, twelve House Democrats, mostly members of the conservative Blue Dog Coalition, voted with Republicans to approve the rules of debate for the Upton bill. The Democrats were Reps. Jason Altmire (Pa.), Sanford Bishop (Ga.), Dan Boren (Okla.), Mark Critz (Pa.), Joe Donnelly (Ind.), Tim Holden (Pa.), Larry Kissell (N.C.), Jim Matheson (Utah), Collin Peterson (Minn.), Nick Rahall (W.Va.), Mike Ross (Ark.) and Heath Shuler (N.C.).