Donald Trump campaigned in Grand Rapids, Mich., on Monday. (Reuters/Carlo Allegri)

Dan Scavino, Donald Trump's director of social media, had a good idea Tuesday morning. Friday's out-of-left-field revelation that the FBI was looping new emails into its dormant investigation of Democratic presidential nominee Hillary Clinton provided the Trump campaign with a believable rationale for arguing that the race had fundamentally changed. (Whether it has, and whether that change is a result of that letter from FBI Director James Comey, is a subject for another article.)

Recognizing that there are some states where you can change your ballot before Election Day, Scavino tweeted out an enticement for voters in several of those states — mostly states where Trump has some conceivable chance of possibly winning — to switch their ballots from Clinton to the Republican nominee.

Here's what this gets right, as an outreach strategy.

1. It pushes out the idea that there are Clinton voters who want to change their votes after the Comey letter. As a reinforcement of the campaign's message, Scavino's tweet is smart. It suggests that this thing is so bad that Democrats are fleeing in droves — hinting, too, that the lamestream media is playing down a significant issue.

2. The net result of a switch is a two-vote swing. If someone switches from Clinton to Trump, that's Clinton minus-one, Trump plus-one — a plus-two shift in the overall margin.

And here's what it gets wrong.

1. The number of people who will find this useful is probably near zero. Shortly after Comey's letter came out, we pointed out that people who had voted by then were more likely to be people heavily engaged in the political process — and therefore strong partisans. After all, people who are undecided about whom to vote for will not vote early, and partisans are far less likely to be undecided about their choice. Research reinforces this. So the number of people who cast a wavering vote for Clinton was probably low.

2. There's no evidence that many people changed their minds after the Comey letter. The Post-ABC tracking poll released Sunday found that most voters didn't think the new Comey letter made them less likely to vote for Clinton — and two-thirds of those who said that it did were Republicans. A poll from Politico and Morning Consult had similar results. Overlay that with the number of Democrats in those swing states who had already voted, and we're talking about fairly small numbers.

I called the Pennsylvania secretary of state to figure out how many people may have tried to switch their votes this week. Wanda Murren, a spokeswoman for the state, said that she didn't have numbers to answer that question. But she pointed out that switching a vote is as simple as walking to the polling place on Election Day and casting a new vote. The absentee ballot would be overwritten.

Which brings us to:

3. The Trump campaign offered unhelpful advice. Scavino's tweet told people interested in changing their votes to call a phone number for Votes PA, a program run by the secretary of state's office. When I called the number, I had to first press "1" for English (p.c. culture!) and then figure out which voting issue I was calling about. Then the phone rang and rang. I was given the chance to leave a message but declined to do so. No one ever answered.

Scavino's tweet could have been, “To change your vote, go cast a new vote on Election Day.” But that, too, isn't the best thing Scavino could have done.

4. Scavino should have encouraged people to visit the Trump campaign website to learn how to change their ballots. This is really simple stuff. Instead of the weird images Scavino used in the tweet, he should have added a link to the website. Then collect information from voters and follow up with an email on what to do. As above, there's probably not really going to be anyone who wants to change his or her vote, so instead of sending that small pool of voters off to call a phone number that is never answered, connect them back to the campaign.

Contrast Scavino's tweet with what the Clinton campaign is doing. It set up a site called “Make a Plan,” which encourages people to plot out how and why they're going to cast a ballot for Clinton next week.

There are researchers who look at what is and isn't effective at getting people to go to the polls. In 2008, David Nickerson and Todd Rogers (of Notre Dame and Harvard universities, respectively) did a study on whether getting voters to articulate their plan to vote in advance made them more likely to vote. When voters were called and asked to walk through their voting plans, turnout increased 4.1 percent over people who'd received a call that simply asked them to commit to going to the polls. In a close race, that increase in turnout can be very helpful, and Clinton's team took it one step further by making the commitment social and aspirational.

At its core, this is not really about Dan Scavino's earnest but flawed attempt to woo Clinton voters. It's about Clinton's dominance in the basic, understood functions of running a campaign, particularly the critical consideration of getting voters to actually vote.

Worrying about having them change their vote is not time very well spent.