President Obama’s “arch nemesis” isn’t Senate Minority Leader Mitch McConnell, said Chris Cillizza in The Washington Post. And it‘s not one of the myriad Republicans pondering a 2012 White House run. It’s conservative talk radio host Rush Limbaugh, who’s “filling a void” where George W. Bush once stood.

Limbaugh sure looks like the “leader of the opposition,” said Jay Nordlinger in National Review. He says what he thinks—and his opinions are sound—“political consequences be damned.” And his refusal to bend to Obama’s popularity has got the president rattled enough to urge Republicans to tune out Limbaugh’s advice. “Keep it up, Rush.”

“Count me as one that is sick of Rush Limbaugh being the only national voice of the GOP,” said Warner Todd Huston in RedState. “Not because I hate Rush or disagree with him much, but because the people we've actually elected” to stand up for conservative principles are standing meekly by while "a mere radio guy" does their job.

As long as Limbaugh is "essentially calling the shots," said Joe Gandelman in The Moderate Voice, the chances for bipartisanship are dim. Conservative Republicans might lap up Limbaugh's "polarizing, attack-dog politics," but it only complicates the GOP's task of broadening its appeal enough to win more elections.