Early in his presidential campaign, Donald J. Trump dismissed political data as an “overrated” tool. But after he won the Republican nomination, his team began building a database that offers a pipeline into the heart of the party’s base, a comprehensive list including the email addresses and cellphone numbers of as many as 20 million supporters.
Now, consultants close to the Trump campaign are ramping up efforts to put that database — by far the most sought-after in Republican politics — to use, offering it for rent to candidates, conservative groups and even businesses.
It is an arrangement that has the potential to help the Republican Party in key midterm races, while providing a source of revenue for President Trump’s campaign and the consultants involved.
It has also set off concerns about diluting the power of one of Mr. Trump’s most potent political assets, while raising questions about whether his team is facilitating the sort of political profiteering that he disparaged during his campaign…
In recent weeks, Mr. Trump’s campaign, which is not known for its adherence to political norms, quietly signed a contract with a newly formed Virginia-based company called Excelsior Strategies to market the emails and cellphone numbers — what is known in the political industry as first-party data.
Excelsior is offering the chance to email Mr. Trump’s supporters at a rate of $35 per 1,000 addresses — or more if the renter also wants to push posts into the Facebook timelines of supporters — according to interviews and marketing emails obtained by The New York Times. The firm has also explored the possibility of clients’ being able to send text messages directly to the phones of Mr. Trump’s supporters, according to the marketing emails and interviews.