At Donald Trump rallies and news conferences, the invocation is very often printed in the cameras' lines of sight to ensure maximum exposure:

Text "Trump" to 88022

If you assumed this is a fundraising ploy, you'd be wrong. The Republican presidential front-runner is self-funding his campaign, remember? (Okay, not exactly, but you're still wrong. There's no donation tacked on to your cellphone bill when you text Trump's name to the specified number.)

Instead of money, Trump ostensibly wants a channel to communicate directly with voters. His website advertises "exclusive updates" for those who subscribe to the texting service.

One problem: Trump doesn't seem to use the service very often.

Two weeks ago, on the day of the Wisconsin primary, I signed up and prepared for The Donald to Make My iPhone Great Again with the exclusive updates I had been promised. Here's how it went.

And then ... nothing for 14 days.

Last week, Fix colleague Philip Bump had the good idea to subscribe using a New York ZIP code (I had used a D.C. area ZIP code) to see whether the Trump campaign might be targeting residents of the Empire State ahead of the primary. He got nothing for five days.

Finally, on primary day Tuesday, the first exclusive updates arrived.

Later, after I asked the campaign about its use  or underuse  of the text line, both Bump and I received this message. (I didn't receive a comment, however.)

What. A. Waste.

Getting voters to sign up for text alerts is a great idea, in theory. Oft-cited research by the digital marketing firm Dynmark International shows people open 98 percent of the text messages they receive. That's an insanely high rate — like triple the open rate for emails. Yet Trump's very limited use of text messaging involves not-at-all-exclusive reminders to vote and ads for his hats.

If Trump actually tried to take advantage of his cellphone database, built by relentlessly promoting his text line through the media, there's a very good chance that subscribers would read whatever he had to say. He could, for example, send a message asking subscribers to signal their levels of support: Text "A" if you're committed to Trump, "B" if you're leaning toward Trump, "C" if you're undecided, "D" if you're leaning toward another candidate, "E" if you're committed to another candidate. Something like that.

Maybe, in another message, Trump could ask subscribers to name the No. 1 issue in the campaign: Text "A" for immigration, "B" for terrorism, "C" for trade, "D" for gun rights.

This kind of voter info could inform customized outreach efforts. If you know a subscriber is leaning toward another candidate and thinks terrorism is the most important issue in the campaign, you can try to bring that voter into the Trump camp by sending additional messages that tout his foreign policy strengths and hammer his opponents' weaknesses.

Here's another idea: When you know voters' ZIP codes, you also know when their primaries and caucuses are — and the registration deadlines. Maybe you could use your text line to remind subscribers to register. While you're at it, you could text Trump's children to remind them to register, too.

At the very least, engaging voters via text could help the campaign identify who backs Trump, who might be persuadable and who is a lost cause. It could add focus to the campaign's turnout efforts.

It is possible to overdo it, of course. Sertan Kabadayi, a marketing professor at Fordham University who has studied text message advertising, said he subscribed to SMS lists for Democrats Hillary Clinton and Bernie Sanders.

"In one case, I got numerous texts almost every day for a while, and they were mostly about donations — nothing different than the emails that they sent me during that time," Kabadayi said. "As you can imagine, I deleted them all. In fact, after a while, I deleted them before even opening them."

That's definitely not what you want. Kabadayi offered some free advice to Trump — or any other candidate who wants to reach voters through text messages.

First of all, don't send some text message with nothing valuable in it. Don't use the SMS messages just like another platform to send the same message that you send through other channels, like your email or Facebook page. However, do not miss out on the opportunities to reach to that receptive audience when you have something new or important to say. There should be an overall message strategy in the first place: What do you want to say to your target audience?

Ryan Buell, a professor in the technology and operations management unit at Harvard Business School, added that Trump text subscribers who expected frequent updates might "feel underwhelmed by the scarcity of updates. They may wonder what’s going on with the candidate, whether the text message service is working, and whether the organization has forgotten about them."

Here's what Buell recommends:

In general, the best practice is to clearly set expectations up front, so that prospective subscribers know the rules of the road and so that they can make an informed decision about what they are opting into. It’s unclear what subscribers who signed-up for “exclusive updates” might be expecting.
Offering different frequency options can also be helpful. Ardent supporters who want the very latest news might sign-up for more frequent messages. Casual fans may opt for less frequent updates, but still wish to be in the loop. Practically speaking, having different tiers also allows those who misforecast their preferences to adjust. Rather than unsubscribing completely, someone who feels they may be hearing too much from the candidate can dial down to a lower level. Those who feel they’d like to hear more, can dial it up.

Right now, Trump is at no risk of making subscribers want to dial down. His campaign goes to the trouble of making sure its text line shows up in press photos and video feeds but seems to be doing little to follow up.

This is part of a pattern. In Iowa, where Trump lost the Republican caucuses to Ted Cruz, his campaign was reportedly inconsistent about contacting the people who attended rallies, despite collecting their information. More recently, Trump has looked like a candidate who loves stumping and winning primaries but can't be bothered to take the next step of electing his supporters as convention delegates — an oversight that could cost him the nomination should he fail to lock it up before Cleveland.

What you see so often on your screen when the Manhattan billionaire speaks — "Text 'Trump' to 88022" — is an emblem of a showbiz candidate who excels at using the media to spread his message and generate excitement but isn't invested in the hard work of grinding for every vote and delegate. He may have gotten away with this laissez-faire attitude in his home-state primary, but squandered opportunities such as this could hurt him in the long run.