Senate Minority Leader Mitch McConnellAddison (Mitch) Mitchell McConnellSenate passes 0B defense bill Overnight Health Care: New GOP ObamaCare repeal bill gains momentum Overnight Finance: CBO to release limited analysis of ObamaCare repeal bill | DOJ investigates Equifax stock sales | House weighs tougher rules for banks dealing with North Korea MORE (R-Ky.) said he would support who ever wins the Republican Tuesday between O'Donnell and Rep. Mike Castle (R-Del.).

"The voters of Delaware are going to decide this very day as we are speaking who they want to represent them in the Senate," McConnell said during an appearance on MSNBC. "I'm going to support the nominee."

Castle is facing a last-minute conservative surge from O'Donnell, the Tea Party candidate who's been backed by former Alaska Gov. Sarah Palin (R) and Sen. Jim DeMint (R-S.C.) and his Senate Conservatives Fund.

O'Donnell is the latest insurgent Republican candidate backed by the Tea Party movement to threaten an establishment candidate, following Sharron Angle in Nevada, Mike LeeMichael (Mike) Shumway LeeOvernight Defense: Senate passes 0B defense bill | 3,000 US troops heading to Afghanistan | Two more Navy officials fired over ship collisions Senate passes 0B defense bill Overnight Finance: CBO to release limited analysis of ObamaCare repeal bill | DOJ investigates Equifax stock sales | House weighs tougher rules for banks dealing with North Korea MORE in Utah and Joe Miller in Alaska. 

The outsider candidates have brought new voters to the primaries and generated enthusiasm, but also may be weakening the Republican party's field of candidates for the general election. Castle argues O'Donnell would lose a general election in Delaware, and polls suggest he's correct. 

McConnell has made clear that he welcomes members of all ideological stripes to the Senate GOP conference, though the new crop of would-be conservative senators is seen as potentially less loyal to him as GOP leader.

"I'm going to support the Republican nominee for the Senate anywhere in America," he said.

That support extends to Alaska, McConnell said, where he said he supported Miller rather than Sen. Lisa MurkowskiLisa Ann MurkowskiSenate Dems hold floor talk-a-thon against latest ObamaCare repeal bill Collins skeptical of new ObamaCare repeal effort How Senate relationships could decide ObamaCare repeal MORE (R), the member of the Senate GOP leadership team to lose in that state's primary.

"She knows I'm supporting Joe Miller," McConnell said. "We expect him to be the next senator from Alaska."