Michael Cohen leaves federal court in New York on Aug. 21 after pleading guilty to charges that include campaign finance fraud related to hush money payments to porn actress Stormy Daniels and ex-Playboy model Karen McDougal. (Mary Altaffer/AP)

Last week, a couple of allegations of high-profile campaign finance violations made headlines. Michael Cohen, President Trump’s longtime personal attorney, pleaded guilty to eight charges, two of which involved illegal campaign contributions. And Rep. Duncan D. Hunter (R-Calif.) was indicted on charges of campaign finance violations ranging from false campaign records to using $250,000 to pay for personal expenses such as groceries, golf, vacations and flights for a pet.

Cohen’s plea bargain implicated the president. In response, several people suggested that campaign finance violations wouldn’t influence voters. For instance, former Utah Republican representative Jason Chaffetz called the allegation “about the weakest thing we could ever come up with on Donald Trump . . . [as] most every other presidential candidate has had some problem or run-in with campaign finance.” A local reporter wrote that the charges against Hunter “might not stop voters in California’s 50th Congressional District” from reelecting him in November.

Do voters care about campaign finance violations? Yes. In new research, we argue that campaign finance violations inform voters’ views about the elected official’s character. Members of Congress who were randomly audited and found to have violated campaign finance law fared about 5 percentage points worse in their general elections than incumbents who were not. So it may be no surprise that once elected officials are tarred with campaign finance violations, they also attempt to win back voters’ trust.

How we did our research

To see whether elected officials who violate campaign finance laws are punished at the polls, we turned to the post-Watergate era, a period much like today, with a president under a cloud of investigations and campaign finance violations frequently in the headlines.

In 1974, Congress amended the Federal Election Campaign Act, creating the Federal Election Commission (FEC), an independent regulatory agency, to oversee campaign finance in federal elections. The FEC hired several auditors from the Government Accountability Office (GAO) to audit elected officials — such as incumbent members of the U.S. House running for reelection — to see whether they were complying with campaign finance laws. But with 435 House elections every other year, the FEC decided to randomly audit a subset of incumbent House members. These audits reviewed 1976 campaign financing, and took place after the 1976 election and before the 1978 election, with results announced to the public.

The FEC found that about half of those audited had major campaign finance violations, including excessive contributions, as  Cohen admitted to this week, and illegal spending, for which  Hunter was indicted. Such violations tell voters that a candidate is, at worst, corrupt or, at best, a disorganized manager.

Political scientist Scott Basinger’s research found that political scandals, like campaign finance violations, did not affect vote share in future elections. That important research did not have the benefit of randomization, since there was no agency randomly auditing legislative behavior.

The FEC’s randomization is key to our study, as it creates an ideal natural experiment for empirical analysis. Randomization allows us to say that the campaign finance revelations violations caused the change in vote share. Consider the way that medical trials compare two groups that look the same, aside from their treatment. The same is true with random audits. There were undoubtedly campaign finance “compliers” and campaign finance “violators” in both groups of legislators, but only those assigned to be randomly audited had their status as a “violator” revealed, while those in the control group did not.

Using this, we compared the general election vote share received by those members of Congress who were audited and found to have violated the law with those who were not audited. We use a method called 2SLS, explained in our paper.

Here’s what we found

We find that on average, audited members of Congress with campaign finance violations did about 5 percentage points worse in their next election than legislators who were not audited. We also considered several district and candidate characteristics that can also affect electoral outcomes, including the vote share the legislator received in the prior election, whether the incumbent faced a quality challenger, whether the incumbent faced a non-campaign-finance scandal, and how much the challenger spent.

Members of Congress who were audited clearly feared a drop in their electoral support, as they increased their attention to their constituents and congressional districts. On average, those who were audited — including those against whom nothing was found — took one more trip home to the district than those not audited. Members found to have violated campaign finance laws took an average of three more trips home. (While we can’t be sure, we suspect that representatives with clean audits worried that they would be punished by voters who could not understand that they were randomly assigned to be audited.) This more frequent travel suggests that these members of Congress felt they needed to pay more attention to their constituents to shore up their support.

Not surprisingly, a later Congress withdrew funding for the FEC audit program — making this a one-time experiment.

Are these results relevant in 2018?

Is it possible that campaign finance violations wouldn’t have such a large effect today? Of course. After Watergate, voters were especially sensitive to corruption, and — since Watergate involved campaign finance shenanigans — may have been sensitive to those violations in particular. Moreover, in the four decades since, partisan polarization has increased dramatically; many people are now more likely to say they will tolerate a corrupt in-party member than a clean out-party member. Basinger’s research, which found no association between campaign finance scandals and vote share, looked at the intervening 40 years.

But we suspect that voters’ reactions to the late 1970s FEC audits remain relevant. Voters didn’t like it when their elected officials violated campaign finance laws back then. Our current political climate has enough parallels to the Watergate era that we suspect voters will react negatively to campaign finance violations again. We will find out Nov. 6.

Abby K. Wood (@yesthatabbywood) is an associate professor of law, political science  and public policy at the University of Southern California.

Christian R. Grose (@christiangrose) is academic director of the USC Schwarzenegger Institute and an associate professor of political science and public policy at the University of Southern California.