Whether the Trump presidential campaign colluded with Russian agents to tip the 2016 presidential campaign is an open question, but there is no doubt of Russian interference.

One of the main ways that Russian agents attempted to influence the election was through tightly targeted ads on social media sites such as Facebook. For example, Facebook has turned over to Congress about 3,000 ads steeped in political dirty tricks. One purported to be in behalf of a nonexistent Muslim group supporting Hillary Clinton, another falsely claimed to represent Black Lives Matter. Facebook alone said it had identified 470 pages and accounts engaged in the activity, which generated about $100,000 in ad revenue.

Identifying the true sources of political advertising is in everyone’s interest. A candidate who benefits from such a campaign today could be stung by it tomorrow. And voters, as a general principle, deserve to know the actual sources of the pitches that they receive.

Wednesday, Sen. John McCain of Arizona became the first Republican to cosponsor the Honest Ads Act, which was introduced by Democratic Sens. Amy Klobuchar of Minnesota and Mark Warner of Virginia. It would create disclosure standards for online political ads.

Congress should approve the bill and use it as a catalyst to eliminate “dark money” by establishing full disclosure of all contributions used for political advocacy.