"There has been barely a squawk from any significant and/or loud Democratic voice over Harry Reid's tax accusations or the new Obama SuperPAC ad," writes Time magazine's Mark Halperin. "And yet when Romney spokesperson Andrea Saul makes some stray, random remark about health care, Rush Limbaugh, Ann Coulter, and Erick Erickson go code red in their criticism of Romney and his campaign."

Halperin is right. When Harry Reid, without any evidence, called Mitt Romney a tax cheat, and when an Obama Super-PAC, equally without evidence, held Romney responsible for the death of an uninsured woman, Democrats and liberals mostly fell in line and stayed quiet. Whatever they thought of their team's down-and-dirty tactics, they didn't speak up.

But after Saul offered a confused-sounding defense of Romney against the Super-PAC ad by approvingly citing Romney's universal health care program in Massachusetts, some of the most prominent voices on the Right let loose. What accounts for the difference?

"It's pretty basic," writes Limbaugh, in response to an emailed question. "The Democrat/liberal side is NOT divided. They are UNIFIED in wanting to destroy conservatives, every time, everywhere. The GOP/conservatives ARE DIVIDED, and the GOP establishment does NOT see the same disastrous threat posed by Obama and the Left that we conservatives see. We are NOT united."

What irked Limbaugh most was not that Saul fumbled her talking points but that she seemed to accept the premise of the Obama Super-PAC attack. "That ad is not about who has healthcare," Limbaugh writes. "That ad is part of the systematic attempt by Obama to DESTROY Mitt Romney, and the concern I have is that our side doesn't even see what's happening."

For her part, Coulter sees a continuing problem with the people who run GOP campaigns. "Republicans are hapless Elmer Fudds, constantly employing people who couldn't care less about the country, but want to be on TV and in spreads for Glamour magazine," Coulter writes in an email. "Who is the Democrats' equivalent of Andrea Saul or the Etch-A-Sketch guy? Name one! The Democrats are focused on winning and hire spokesmen who don't make constant unforced errors."

Finally, Erickson sees holding Romney to account as a matter of keeping candidate and campaign on a conservative path. "The GOP is more often open and consistent, and the Democrats fall in line," he writes. "I realize there are plenty on our side who disagree with me, but I think if we are not consistent in our criticisms of the Romney campaign when they go off the reservation, they'll take the silence as permission, once elected. Barack Obama sure did with the Left."

As influential as they are, Limbaugh, Coulter and Erickson don't set the agenda for Republicans. But their reactions underscore the continued fragility of Romney's relationship with the conservative world. When Romney hews to a strongly conservative line, he is fine. But when the former Massachusetts governor sends any signal -- a poorly worded phrase, a staffer's mistake -- that sounds like something a conservative would not say, some of his critics on the right immediately recoil and say, "See -- I knew he wasn't one of us."

Romney has grappled with the problem from the moment he entered national politics. This year, it accounted for one of the more awkward moments of the campaign, his February speech to the Conservative Political Action Conference in which he used the word "conservative" more than 20 times and noted that he was "a severely conservative Republican governor" in Massachusetts.

Many Republicans hoped the problem would go away in the general election campaign. After all, in the primaries Romney was trying to convince mostly conservative Republicans that he was a better candidate than his mostly conservative rivals. Now, as Romney runs against President Obama, many supporters hoped Romney would face fewer calls to prove his conservative bona fides.

But the problem hasn't gone away. And it will likely flare up again in the future, when Romney messes up the answer to a question or one of his aides mangles an appearance on television.

The worries expressed by Limbaugh, Coulter and Erickson aren't nit-picking. They are concerns about the very nature of Mitt Romney and the people he has chosen to run his campaign. Maybe those concerns are mistaken or misdirected. But Limbaugh is right: At this moment, deep down, Republicans and conservatives are not united, not under Mitt Romney or anyone else.

Byron York, The Examiner's chief political correspondent, can be contacted at byork@washingtonexaminer.com. His column appears on Tuesday and Friday, and his stories and blogposts appear on washingtonexaminer.com.