Senate Minority Leader Mitch McConnellMitch McConnellThe Memo: Winners and losers from the battle over health care GOP senators pitch alternatives after House pulls ObamaCare repeal bill Under pressure, Dems hold back Gorsuch support MORE (R-Ky.) is facing sharp attacks from conservatives for opposing Sen. Ted CruzTed CruzHow 'Big Pharma' stifles pharmaceutical innovation AIPAC must reach out to President Trump Under pressure, Dems hold back Gorsuch support MORE's (R-Texas) effort to defund ObamaCare in the Senate.

But the Kentucky senator, who is facing an aggressive primary challenge in 2014, is betting the attacks won't gain traction among Republican voters because they're couched in complicated legislative maneuvering that may be difficult for outside-the-Beltway voters to follow. 

The political sparring centers on McConnell's decision Monday to oppose a Cruz-backed attempt to hold up a Senate vote on House legislation defunding President Obama's signature healthcare law.

Cruz, who supports defunding ObamaCare, wanted to block Senate consideration of the House measure to prevent Reid and Democrats from gutting the provisions stripping funding for the Affordable Care Act. 

McConnell said he would not join Cruz in blocking the bill from coming to a final vote, because it includes the very language sought by conservatives to eliminate ObamaCare funding.

The Republican leader also insisted he would vote against any measure from Senate Majority Leader Harry ReidHarry ReidThis obscure Senate rule could let VP Mike Pence fully repeal ObamaCare once and for all Sharron Angle to challenge GOP rep in Nevada Fox's Watters asks Trump whom he would fire: Baldwin, Schumer or Zucker MORE (D-Nev.) to strip the defund provision from the law - a move that could give him political cover with the GOP base. 

But Matt Bevin, the conservative challenging McConnell for the GOP nomination in Kentucky's Senate race, said McConnell — by not trying to block Democrats — has in fact turned his back on Republicans trying to stop ObamaCare.

"Like so many other crucial fights, Mitch McConnell has caved to Harry Reid on ObamaCare and is refusing to fight to defund this disastrous legislation," Bevin said a statement issued Tuesday.

The Senate Conservatives Fund (SCF) called the senator's opposition to Cruz's gambit was "the ultimate betrayal" of conservatives. The group, which has hit McConnell before for refusing to sign onto the ObamaCare strategy, also lashed out at Sen. John CornynJohn CornynGOP senators pitch alternatives after House pulls ObamaCare repeal bill Rand Paul takes victory lap on GOP health bill Senators push Trump on defense deals with India MORE (R-Texas) for not backing the effort to tie the threat of a government shutdown to defunding the Affordable Care Act. 

"We knew Mitch McConnell and John Cornyn weren't with us when they voted to fund ObamaCare earlier this year. But then, under pressure from grassroots, they said they supported the effort to defund it. They even ran political ads in their home states to make voters think they were on their side," said SCF Executive Director Matt Hoskins. 

"But now, faced with the prospect of having to fight for the things they claim to believe, these Senate leaders have surrendered."

Whether McConnell takes a political hit from conservatives depends, in large part, on whether ObamaCare opponents in his state understand the procedural maneuvering set to occur in the Senate. 

"Senator McConnell supports the House Republicans' bill and will not vote to block it, since it defunds ObamaCare and funds the government without increasing spending by a penny," McConnell spokesman Don Stewart said Monday in a statement. "He will also vote against any amendment that attempts to add Obamacare funding back into the House Republicans' bill." 

Longtime Republican strategist Ron Bonjean, who worked for then-Senate Majority Leader Trent Lott (R-Miss.), said he expects McConnell to "walk away from this fight unscathed."

"The challenge for conservatives who are opposed to this is explaining why voting to defund ObamaCare was a bad thing," he said. 

"You've got some conservatives that are upset and would like him to do this special legislative maneuver that wont make a lot of sense to Beltway outsiders. Most primary voters are going to be very confused because Sen. McConnell's technically voting to defund ObamaCare."

Bevin, however, said McConnell's opposition to Cruz's gambit amounts to taking the same position as Kentucky Democratic Senate candidate Alison Lundergan Grimes.

"There is really no difference between Mitch McConnell and Alison Grimes — both would vote on the side of Harry Reid," Bevin said. 

"I am proud to support conservatives like Sen. Ted Cruz in his fight to defund ObamaCare, and I promise the people of Kentucky: I will never cave to Harry Reid."

McConnell's campaign didn't respond to Bevin's attacks and instead hit Lundergan Grimes in a statement, touting the senator's opposition to ObamaCare and suggesting that a vote for Lundergan Grimes would be a vote in support of the healthcare law.

— Updated at 12:51 p.m. and 3:33 p.m.