Washington (CNN) -- Dark theories about President Barack Obama's citizenship show no signs of fading away.
But "birthers," as those skeptics of Obama's heritage are known, no longer seem relegated to tinfoil hat fringes of American politics.
Instead, it's Republican members of Congress, elected officials and state party organizations -- in Arizona, Iowa and Florida -- that are responsible for the latest round of conspiracy-mongering. And the loose talk could cause a headache for Mitt Romney this election season.
The issue flared this week in Iowa, a closely watched electoral battleground, where the state GOP wrote a passage into its proposed party platform calling on presidential candidates to "show proof of being a natural-born citizen," beginning with the 2012 election.
Don Racheter, chairman of the Iowa Republican Party's platform committee, told Radio Iowa that the language was intentionally crafted as a "shot" at Obama.
"There are many Republicans who feel that Barack Obama is not a 'natural-born citizen' because his father was not an American when he was born and, therefore, feel that according to the Constitution he's not qualified to be president, should not have been allowed to be elected by the Electoral College or even nominated by the Democratic Party in 2008," Racheter said defiantly, even though the language may be tweaked at next month's Iowa GOP convention.
Birther theories vary.
Some argue Obama was born in Kenya, not Hawaii. Others, such as the one outlined in Iowa, focus on the fact that Obama's father was not a U.S. citizen, supposedly rendering his son ineligible for the Oval Office.
The Romney campaign would clearly prefer to focus on the economy and banish birth certificate talk to the "fever swamps" of the Internet, as Buzzfeed's Ben Smith recently labeled the sinister corners of the Web where conspiracy theories thrive.
Instead, birtherism is creeping more and more into the domain of GOP officialdom.
Fresh examples appear on a near-weekly basis, often in key battleground states, much to the delight of Democrats eager to distract voters from the troubled economy and tie Republican candidates to the extreme elements of their party.
Republican members of Congress in swing states such as Florida (Rep. Cliff Stearns), Colorado (Rep. Mike Coffman) and Missouri (Rep. Vicky Hartzler) have publicly raised questions about Obama's citizenship in recent weeks.
In North Carolina, the state GOP convention will be headlined next week by Donald Trump, whose 2011 crusade to unearth details about Obama's origins drew global attention and prompted the White House to release the president's long-form birth certificate.
The Romney campaign has since leveraged Trump as a campaign surrogate and fund-raiser.
Also in North Carolina, a state both campaigns are aggressively targeting, The Charlotte Observer recently retracted its endorsement of a Republican congressional candidate after he said he was "suspicious" of Obama's birth certificate.
In Arizona -- not quite a swing state, but one that national Democrats are nonetheless keeping an eye on -- Secretary of State Ken Bennett said last week that he may refuse to put the president on the ballot in November unless the state of Hawaii authenticates Obama's birth certificate.
Bennett, a co-chairman of Romney's Arizona campaign, said he was only doing so at the request of his constituents.
On Wednesday, Bennett said that he had received the necessary verification from Hawaiian officials. "They have complied with the request and I consider the matter closed."
With the general-election fight between Obama and Romney now under way, and with both campaigns fighting for an increasingly tiny share of undecided and moderate voters, Republicans are expressing frustration and downright embarrassment that the issue won't just fade away.
"Birtherism is a fringe issue that's way out of the mainstream, and it's disturbing when you see people you ... have some level of respect for, whether it's members of Congress or even Donald Trump, falling into that category," said Steve Schmidt, one of Sen. John McCain's senior advisers in 2008. "In the middle of the electorate, people think it's bats--t crazy. The side that's seen flirting with it doesn't do themselves any favors."
GOP strategist Rob Johnson, a political adviser to Texas Gov. Rick Perry, called the ongoing questions about Obama's background "an unnecessary and unfortunate distraction."
"We need to continue our focus on the president's record and Gov. Romney's plans to get the country working again," Johnson said.
Both Romney and Republican National Committee Chairman Reince Priebus, trying to keep the campaign focused on the slow-moving economic recovery, have rejected birther theories.
"I've been pretty clear now for over a year ... that this issue is a distraction," Priebus told CNN's John King on Tuesday night. "We have everything we have to have on this president."
Even the late conservative provocateur Andrew Breitbart -- whose eponymous website recently uncovered a 1991 brochure from Obama's literary agency claiming, inaccurately, that Obama was born in Kenya -- said "the birther thing" is "ridiculous."
But the conspiracies continue to percolate and wiggle into the mainstream, raising the prospect that Romney will be asked about Obama's heritage by a voter at a town-hall meeting during the heat of the campaign, or about the latest local birther flap by a reporter in Nevada, Ohio or elsewhere.
McCain faced that uncomfortable situation repeatedly during his presidential campaign four years ago.
At one memorable October 2008 town hall in Minnesota, an elderly questioner called Obama "an Arab."
McCain reached for the microphone to correct the woman and defended Obama as "a decent family man."
The moment was one of many that threw McCain's campaign, then in its final sprint, wildly off-message.
"If 10% of your audience is primed to ask a crazy question, the risk of undermining your message is exceedingly high," said Schmidt, the former McCain adviser. "You can't turn over control of the campaign's message on stuff like this."
In an era in which the political media is eager to spotlight "outrage" and the "craziest stuff happening that day in the American public space," Schmidt said that Romney's tightly disciplined campaign team has to be careful about handing the town-hall microphone over to the conservative base.
"The reality is we live in very serious times," he said. "Mitt Romney is going to have to a strategic imperative to deliver an economic message every day. And every day he is not is a bad day for him."