New York (CNN) The US's largest election equipment manufacturer has begun quietly lobbying Congress to force all voting equipment to create a paper trail, a sharp departure after years of selling paperless digital machines that can't be fully audited. The change of stance comes amid concerns over the security of elections following Russia's interference effort i n the 2016 presidential election.

"There's a big recognition today that auditing is important, and to do a proper audit you need a piece of paper," Kathy Rogers, Election Systems & Software senior vice president of government relations, told CNN.

"I'll tell you it's a decision that came at a cost. We've lost a few sales because of it. But we think it's the right thing to do," Rogers said.

Voting experts resoundingly agree that while no system is perfect, the only way to reliably audit an election is to compare results with a physical tally of paper ballots.

President Donald Trump has appeared to agree when he told reporters last month that "going to good, old-fashioned paper, in this modern age, is the best way to do it."

Election security was largely seen as a niche issue before the 2016 presidential contest. Since then it's been revealed that Russian intelligence officers successfully hacked the Illinois voter registration database and two Florida counties' networks

'Meaningful step'

"It's a meaningful step for the election systems industry compared to where we were two years ago, when 'just trust us' and 'hackers will be sued' seemed to be the industry's public position on election security," said Maurice Turner, a senior technologist at the Center for Democracy and Technology.

Election Systems & Software made the decision to stop selling paperless machines late last summer. But the company did not immediately publicize the change and around the same time got into a public fight with researchers at the DEF CON hacker conference, who spent several days finding vulnerabilities in Election Systems & Software machines.

Starting in October, the company ramped up its meetings with lawmakers, passing around what Rogers calls the "American flag document," a four-page flyer for the company that says it has "staked its reputation on the security of our products."

In March, the company rented a room at the Reserve Officers Association, right by the Capitol, and invited staffers from the House Homeland Security and Senate Rules committees to test its equipment.

Despite Russia's interference in 2016, Congress hasn't passed any legislation to improve election security since, save allocating $380 million for machine upgrades in a spending bill last year.

Letting the market decide

Since 2016, lawmakers have introduced dozens of bills to promote election security. But lawmakers have indicated that the most likely action in the Senate this year would be an additional influx of cash for state and local governments to buy new equipment

Senate Majority Leader Mitch McConnell has refused to bring any of the bills to a vote.

A spokesperson for the Kentucky Republican declined to comment but referred to remarks McConnell recently made to reporters where he noted that "very few of you have written about is the absence of problems in the 2018 election. I think the Trump administration did a much, much better job working with state and local officials in the last election. Remember, the one that generated all the problems was 2016."

But the US intelligence community disputes the notion that just because the 2018 election was relatively free from blatant foreign interference means the problem is solved.

"I think we recognize that our adversaries are going to keep adapting and upping their game," FBI Director Christopher Wray said in April. "And so we're very much viewing 2018 as just kind of a dress rehearsal for the big show in 2020."

Though he's opposed to the elecion security bills, McConnell hasn't ruled out another influx of money to replace equipment, letting the industry dictate security changes on its own.

On Tuesday, Senate Minority Leader Chuck Schumer said, "Democrats are determined not to let Leader McConnell and Senate Republicans sweep the issue of securing elections from foreign interference under the rug." He articulated only one plan, however: "to push for more election security money."

Earlier this month, Election Systems & Software CEO Tom Burt wrote an op-ed calling for Congress to make paper ballots the law, something that would have been unthinkable a year ago.

The company itself doesn't endorse any of the election security bills -- instead, Rogers said, "The tenets of any piece of legislation that call for paper-based systems and audit, we 100% support."

But critics say Election Systems & Software's open pivot to paper is simply marketing, after the company saw that paperless machines were on the way out.

"After years of selling voting equipment that it knew was insecure, and fighting tooth and nail against real election security, ES&S is finally admitting that paper ballots are the most secure system currently available," Sen. Ron Wyden, whose PAVE Act is one of the strictest security bills introduced in the Senate, told CNN in a statement.

"If it is serious about this change of heart, ES&S would tell its friends in Georgia and Speaker McConnell to stop standing in the way of the PAVE Act's common-sense requirements to protect American democracy," the Oregon Democrat said.

Kay Stimson, the vice president of government affairs at Dominion, one of Election Systems & Software's closest competitors, expressed surprise at Burt's op-ed, saying her company had met those requirements.

"All Dominion-manufactured systems produce paper," she told CNN. "Our company has never opposed requirements for paper records, nor were we aware of other companies previously advocating against such requirements."

Last week, South Carolina, a state whose long-standing dependence on paperless voting machines caused it to be consistently ranked as one of the country's worst for voting security, announced a new $51 million contract with Election Systems & Software.

"It's not weird," Susan Greenhalgh, the policy director at National Election Defense Coalition, told CNN. "They want more money to push people to new voting equipment that they get to sell. They developed a marketing strategy where they could make more money selling paper."