We’ve already seen that the right’s push to shut down the government to defund Obamacare has become an issue in the Kentucky Senate GOP primary, with Tea Partyer Matt Bevin regularly deriding Mitch McConnell as a liberal squish over his failure to hop aboard the Ted Cruz Shutdown Express to Nowhere.

Now the defund-Obamacare battle is flaring up in Louisiana, among Republicans challenging Senator Mary Landrieu, one of several vulnerable red state Dems.

Two Republicans in that race — GOP Rep. Bill Cassidy, a physician, and Rob Maness, a former member of the Air Force and self-described “true Constitutional conservative” — have been showcasing their anti-Obamacare cred, with the question of the push for a shutdown at the center of their duel.

Cassidy is regarded as the far more prominent opponent (Maness polls far, far behind), but as National Journal notes, the state’s unusual election rules, in which all candidates are on the general election ballot, may require Cassidy to “protect his right flank.”

Cassidy has been very vocal against Obamacare, but he revealed his liberal squishiness earlier this week when he clarified that he doesn’t support a shutdown to force the defunding of the law if it results in stopping payments to the military. However, Cassidy toughened up his stance by signing a letter released yesterday by 80 House Republicans calling on GOP leaders to defund the law.

Still, Maness has challenged Cassidy to prove his anti-Obamacare bona fides by supporting a shutdown, just as Bevin has been doing of McConnell, tweeting: “you say you oppose Obamacare? Then why would you vote to fund it as Senator?”

Cassidy’s bid for anti-Obamacare cred, meanwhile, is complicated by an inconvenient problem. The NoLa Defender reports that as a candidate for state senate in 2007, he campaigned on a platform that included creating a statewide health insurance exchange similar to what the Affordable Care Act creates, and subsequently authored a bill along those lines.

The backdrop to this is that Landrieu, who is viewed as perhaps the strongest of all vulnerable red state Dems this cycle, continues to proudly tout her vote for the Affordable Care Act, even though Republicans predict Dems will scurry away from the law once implementation proves it’s a disaster, which just has to be inevitable.

So keep an eye on how this plays in various races. Maybe you can’t be too anti-Obamacare in a red state or district. But it may also prove that supporting the most extreme measures available to block the law — even as anti-Obamacare mania forces GOP primary combatants ever further to the right — could undermine efforts to make a sane case against it, ultimately making it harder to turn it into a serious vulnerability.