Imagine for a moment that it's September 2018. The midterm elections are heating up, and you've decided you want to do absolutely anything you can to make sure your member of Congress is not re-elected. Well, good news: If you have a credit card and a Facebook account, there's a way you can spend unlimited amounts of money to do just that -- and there's no law, no regulation, no mechanism of any kind to stop you.

Offline, there are laws and rules about campaign spending and donations that are enforced. You can't give a candidate more than $2,700 in a cycle. If you want to run a TV ad, you need to be careful about what you actually say in the ad, and disclose that it is an ad and who is responsible for it.

Facebook and its competitor social networks, though, are part of a largely unregulated Wild West of political spending, a reality to which legislators and regulators are only now starting to awaken, after the disclosure that a Russian troll farm purchased $100,000 worth of ads on Facebook during the 2016 election.

Facebook CEO Mark Zuckerberg said on Thursday that he wants to make political ads on the platform "more transparent" -- in other words, for the most part, making them more like campaign ads on TV, where they come with a disclaimer identifying who is responsible for them.

Related: Facebook says it will hand Russian ads over to Congress

However, unlike TV, many of the political ads purchased on Facebook don't fit the traditional definition of a "political ad." And even after Zuckerberg's announcement, Facebook hasn't said what exactly they'll term a political ad that must come with a disclaimer and be made public. At least some of the $100,000 worth of politically-themed ads linked to a Russian troll farm purchased during the 2016 election that Facebook has disclosed, which according to what Facebook has said were not traditional campaign ads, may not have been subject to any of the new policies Zuckerberg described.

Unless Facebook is planning a far more radical change to its business than it has suggested so far, if you wanted to, you could go on the site tomorrow and spend unlimited sums making sure that people see a story harmful to the chances of a candidate you oppose and it would likely go unchecked. A major donor with a few hundred million dollars burning a hole in their pocket could do the same.

Facebook and the government have less than a year to go before the midterms. If they want to take truly meaningful action, time is running out. But some campaign professionals are skeptical that the Federal Election Commission could effectively answer all the questions involved in regulating digital advertisements -- starting with fundamental issues of identifying what, exactly, counts as a political ad in a world where individuals and organizations can pay to promote news stories, op-eds, memes, videos and other messages.

"Facebook specifically has done a terrible job with an impossible task. This is a really hard thing to do, and they suck at it," said a senior Republican digital ad buyer who -- like others interviewed for this story -- did not wish to be named due to the sensitivity of the issue.

People on the other side of the aisle agree.

"With no requirement on the part of the internet companies to make political ad spending public, the door is left wide open for bad actors to come in and buy advertising," said Oren Shur, the director of paid media for Hillary Clinton's 2016 presidential campaign.

"That's what we saw happen with the Russians on Facebook, and it wouldn't be surprising if it's happening in other places too," Shur said. "The gaps in the current law basically invite it."

On TV, in the pages of a newspaper, or on a yard sign, there's no question about what an ad is. But on Facebook, things are different.

The dominant form of advertising on Facebook is its Sponsored Posts, which are posts that any owner of a Facebook Page can pay to promote so that people who do not follow the Page will see them. These posts can be regular ads, but they don't have to be. Media organizations, for instance, will often pay to promote their articles or videos -- so if you see, say, an article from the New York Times, the Wall Street Journal, CNN, or any number of other media outlets showing up in your feed even though you don't follow that outlet and none of your friends shared the article, that's what happened.

Related: Facebook is planning big changes to political ads on its site. Are they enough?

Any Facebook user can set up a Facebook Page, and any page owner can run ads. And a page doesn't have to own the content it promotes.

This makes sense in the context of a Page promoting a product -- it allows, for example, a meal kit service to promote a positive review of their wares.

In the context of an election, that same system means that anyone can set up a page and start getting the message out about a given race, and they don't even have to go to the bother of producing anything. They can promote a positive article about the candidate of their choice, or a negative one about that candidate's opponent. They can focus solely on promoting accurate articles from the most reputable sources, or they can promote objectively fake news stories, assuming they can get around the steps Facebook has taken to deal with the problem of fake news.

And when they do that, they have access to a powerful tool in Facebook's user-targeting software. If they've read in their local newspaper that their candidate is struggling among males in their twenties in a particular county, or that their candidate's opponent needs to hold on to women with college degrees, it's possible to target groups like that specifically.

The identity of the people running a page is only known by Facebook. And even then, it's not too difficult to set up a Facebook page using a fake name.

U.S. election law makes it illegal for non-U.S. citizens outside the country or those here who don't have at least a Green Card to spend money to influence an election, but there's little to actually stop them from doing so on Facebook.

On top of this, there is less transparency about ads online than there is elsewhere.

Broadcasters are required to keep records of the political ads they run on their air and who pays for them. No such register exists in the digital space.

And while a television ad will likely be seen by a broad group of people -- including political opponents, who can respond, and members of the media, who can fact-check -- that's not always the case on Facebook.

Facebook allows pages the options of what it calls "unpublished page posts," which observers sometimes refer to as "dark posts." This type of post never actually appears on the page; it can be seen only by the users at whom it is targeted. A narrowly targeted dark post, reaching only a small subset of voters, might never be seen by anyone who could fact-check it, or who would have an interest in doing so, allowing a misleading or false message to spread.

Zuckerberg said Thursday that Facebook would no longer allow this for political ads, but Facebook has not said whether this policy change would also capture ads intended to affect the election that do not actually look like typical campaign ads.

Some people in Washington are starting to sound the alarm about all the ways that Facebook could be used in an election.

On Wednesday, a group of congressional Democrats sent a letter to the FEC asking the commission to look into new rules to prevent foreigners from using social media to interfere in elections. And two Democratic senators, Amy Klobuchar and Mark Warner, are preparing to introduce legislation that would among other things require disclaimers noting who paid for advertisements on social media.

Related: Democratic senators preparing bill to deal with online political advertising

FEC Commissioner Ellen L. Weintraub, a Democrat, wrote in a letter to her fellow commissioners last week that the agency needs to "revise and modernize" its internet disclaimer regulations. Those regulations are intended to require disclaimers on political ads online, however they have not kept pace with the nuances of digital advertising, particularly on social media. In 2010 Google was given an exception, and when Facebook sought an exception, the FEC was deadlocked and thus no advisory was issued. Currently, Facebook does not show disclaimers on its ads.

But if they do decide they want to take some action, legislators and regulators will first have to decide what even counts as a political ad, and whether simply promoting an article fits the definition.

Then, there's the question of identifying who is spending money on political ads. Campaigns and party committees are easy -- but bad actors could also funnel political advertisements through other Facebook Pages. And even if the owner of those Pages disclosed paying for the ad, the Republican ad buyer said, "nobody knows whether you did that because you actually believe it or someone put $50K in your Swiss bank account."

Hovering over all of this, the source said, is a sense that the FEC -- which still allows Senate candidates to file campaign finance reports on paper, rather than electronically -- is no match for a rapidly changing advertising world in which politicians and advocacy organizations are increasingly able to decide to which individuals' screens their message is delivered.

On Tuesday, CNN put the following to Facebook: "A lack of regulatory oversight and the capabilities offered by Facebook's advertising platform means that the social media network could easily be weaponized during next year's midterm elections -- by actors both inside and outside the US."

In response, the company said, "We are looking into more ways to address ad transparency on our platform."

On Thursday, Zuckerberg outlined part of that vision.

But for Facebook, for regulators, and for American voters, time is running out.