(CNN) A bipartisan trio of senators unveiled legislation Thursday that would place new disclosure requirements on political advertisements in an effort to combat the kind of election meddling that Russia engaged in during the 2016 election campaign.

The bill from Democratic Sens. Mark Warner of Virginia and Amy Klobuchar of Minnesota would require the same disclosure for online political ads that is currently in place on ads that appear on television and the radio. They said at a news conference Thursday that the legislation would update US laws so that online political ads had the same protections against foreign interference as traditional ads.

"We need regulatory rules, a framework, that shields our elections from foreign money," Klobuchar said. "If a candidate or a cause buys an ad on TV, the same rules should apply if they buy it on Facebook or Google or on Twitter."

Sen. John McCain, an Arizona Republican, has joined their effort and is co-sponsoring the bill, giving it a bipartisan boost in the Republican-controlled Congress.

"I've been for full disclosure for the last 25 years," McCain said in explaining why he was backing the bill.

The legislation is an outgrowth of the congressional investigations into Russia's election meddling, which has taken a major interest in Russia's use of social media platforms. Warner is the top Democrat on the Senate intelligence committee, one of three panels looking into Russian activity tied to the election.

Facebook has turned over 3,000 paid political ads purchased by Russian-linked accounts to the House and Senate intelligence committees that which showed efforts to sow discord in the US with posts on Black Lives Matter, gun rights and more. Facebook has said that 470 Russian-linked accounts purchased $100,000 worth of ads.

Officials from Facebook, Twitter and Google are testifying publicly before both the House and Senate intelligence panels on November 1.

The bill would require digital platforms with at least 50 million viewers monthly to maintain a public file of all political ads purchased above a $500 threshold. The legislation also requires online platforms to "make all reasonable efforts" to ensure that foreign individuals are not purchasing US political ads.

The $500 threshold is much lower than what was initially considered when the senators were drafting the bill. In a letter sent to senators last month, Warner and Klobuchar wrote that their bill would require all major digital platforms to keep a public record of groups or individuals that make ad buys of more than $10,000, in line with television and radio ads.

The threshold was lowered because digital ads are much cheaper, Warner said.

Warner has said that the ads Facebook disclosed were just the "tip of the iceberg" of Russia's election interference via social media, and he's slammed Twitter for the limited scope of its internal investigation into the matter. He argued that the bill introduced Thursday was a "light touch" approach to regulating the social media companies.

The senators are introducing their bill with an eye toward getting new laws in place ahead of the 2018 midterm elections, warning that Russia is poised to once again seek to meddle in the US campaign.

But it's not yet clear how quickly the bill would move or if it has support among key Republicans.

"I have a hard time understanding how you do legislation on social media platforms before you have them in for a hearing," Senate Intelligence Chairman Richard Burr, a Republican, told CNN on Thursday. "What I understood they were trying to get at is already illegal: foreign money in US elections. ... I just want to make sure that we don't have a belief that we've solved a problem that I think is going to be continually exploited by (the Russians) and potentially others."

It's also unclear where the social media giants will land on the bill once the details are released. Facebook chief operating officer Sheryl Sandberg made the rounds on Capitol Hill last week, meeting with top Republicans and Democrats as well as the Congressional Black Caucus and Congressional Hispanic Caucus.

"We stand with lawmakers in their effort to achieve transparency in political advertising," Erin Egan, Facebook's vice president for US public policy, said in a statement. "We have already announced the steps Facebook will take on our own, and we look forward to continuing the conversation with lawmakers as we work toward a legislative solution."

Facebook CEO Mark Zuckerberg announced last week that the social network would begin voluntarily requiring disclaimers on political ads that appear on the site. But in 2011, Facebook went to federal regulators to get an exception from a rule that would have forced it to do the same thing.

Warner and Klobuchar said they were working with the companies and think the legislation is stronger than when they began, but also argued that voluntarily disclosing political ads would not cut it.

"I'm not going to tell you they support this bill right now, but they have to realize that as the world has changed and they have been selling ads to people and making money off of this political system, that they have an obligation just like TV and radio has to disclose this publicly," Klobuchar said.

One of the key questions is whether accounts would be able to evade any new disclosure requirements, which explains why the senators lowered the $10,000 ad disclosure threshold to $500.

Of the thousands of Russian-bought Facebook ads, Facebook has said less than $3 was spent on half of the ads. For 99% of the ads, less than $1,000 was spent. According to Facebook, someone buying an ad for $33 — the average cost suggested by the $100,000 the Russians spent on roughly 3,000 ads — could expect to reach between 11,000-63,000 users in one day.

An ad-buyer could reach up to almost 4 million Americans in 24 hours by spending $9,999 — a dollar under the $10,000 limit — according to estimates on Facebook's ad platform reviewed by CNN.