Senate Democrats harried electronic cigarette companies throughout 2014, pushing hard for new rules and restrictions on the booming multibillion-dollar industry. Now, congressional Republicans - fresh off a November election landslide - are standing up for e-cigarettes and pushing back on pending regulations critics fear may allow administrative product bans.

House Speaker John Boehner, R-Ohio, House Majority Leader Kevin McCarthy, R-Calif., and House Energy and Commerce Committee Chairman Fred Upton, R-Mich., wrote to Health and Human Services Secretary Sylvia Burwell last week requesting a change to proposed Food and Drug Administration regulations that may be enacted soon.

The proposed rules, released in April by the FDA, an HHS division, would require e-cigarette manufacturers to win “premarket” approval for their products within two years or pull the items from the market.

The new tobacco product approval process would apply to e-cigarette products released after February 2007, the proposed rules say, meaning nearly all e-cigarettes currently on the market would undergo rigorous review.

“[M]ost e-vapor products did not exist at that time,” the House Republicans wrote to Burwell. “FDA did not even consider e-vapor products to be tobacco products until 2011.”

The leaders wrote that “[a]s a practical matter, many newly deemed products could be removed from the market” if the 2007 date is not changed.

The premarket approval process - pursuant to the Tobacco Control Act of 2009 - requires significant time and expense for companies, and a favorable FDA ruling is not guaranteed. Conventional cigarettes, generally accepted as more hazardous to users’ health than e-cigarettes, were grandfathered into the regulatory framework and did not undergo premarket vetting.

Boehner, a well-known user of conventional cigarettes, and his colleagues said the proposed rules put e-cigarettes and some cigars at a disadvantage against older nicotine offerings such as cigarettes and loose tobacco.

The House Republican leaders ask that existing e-cigarette products be allowed to remain on the market, with a grandfathering date of either when rules are formalized or the April 2014 date the rules were proposed.

"The secretary appreciates hearing from members of Congress," a Health and Human Services spokesperson tells U.S. News. "HHS looks forward to responding to the letter."

Gregory Conley, president of the American Vaping Association industry group, says many people don’t appreciate the stakes. He notes the Tobacco Control Act is sometimes called “the Marlboro Protection Act” because it grandfathered in existing tobacco products while making it nearly impossible for small firms to introduce new items.

Conley says e-cigarette manufacturers likely would need individual applications for each e-cigarette device and each e-liquid flavor option - a burden multiplied by different nicotine concentrations.

If the rules are adopted with the 2007 date, Conley expects the FDA to use its authority to arbitrarily ban flavor options and devices.

Companies seeking premarket approval for new tobacco products must submit an application including a list of ingredients, descriptions of manufacturing and product use, and proof the product marketing is “appropriate for the protection of the public health."

The FDA predicts e-cigarette companies will spend roughly 5,016 hours per application, with an estimated compliance cost of roughly $300,000 for each submission. Consumer and industry groups say this burden disadvantages small companies who offer a diverse range of devices and e-liquid in various flavors and nicotine concentrations and may force them out of the market, benefiting brands owned by Big Tobacco that offer non-refillable devices with traditional cigarette flavors.

Conley points out if the date is moved forward to coincide with implementation, all existing flavors would be allowed. If a company wanted to introduce a new flavor, he says, they would face a much lower standard for FDA approval, a less-strenuous substantial equivalency application, showing that similar flavors are already on the market.

“If you don’t move up the grandfather date, then the FDA is never going to [give premarket approval] for a flavored e-cigarette product - that will be their backdoor prohibition on almost all flavors,” he says. “Maybe they’ll approve a scotch or whiskey, but they won’t approve the flavors I like.”

Many e-cigarette users zealously defend their preferred candy- or fruit-flavored e-liquid against claims from politicians and health advocates that these options are intended to appeal to children.

A survey conducted earlier this year by the E-Cigarette Forum website found 79 percent of 10,000 respondents would "look to the black market" if products they use are banned. E-cigarette users can already blend their own flavors using commercially available food flavoring - a practice almost certain to expand in response to restrictions.

Most e-cigarettes work by heating a liquid comprised of tobacco-derived nicotine, propylene glycol, vegetable glycerin and flavorings. Propylene glycol and vegetable glycerin are not carcinogenic when ingested, but the long-term health effects of inhaling the liquids is not known and at least one peer-reviewed study has found high-voltage e-cigarettes can produce cancer-causing formaldehyde.

Though House Republicans are criticizing the proposed rules as too far-reaching, several Senate Democrats were upset by what they considered relatively modest rules, which also include a nationwide minimum age limit and a ban on free samples.

The FDA accepted more than 70,000 public comments through August for its rules proposal and can at any time promulgate the rules as proposed, modify and enact the rules or re-issue proposed rules with a new public comment period.