T-Mobile and Sprint may be getting close to a merger. Here’s what you need to know.

In 2014, Sprint tried to buy T-Mobile in a deal that ultimately fell apart under scrutiny by the Justice Department and the Federal Communications Commission. Regulators at the time concluded that having four major competitors in the cellular space, not three, would do the most to preserve competition and help consumers. Analysts say that a new agreement between the two companies would likely hand the reins to T-Mobile, which overtook Sprint in 2015 as the nation's third-biggest carrier. Given that T-Mobile was behind the push for many of the industry changes we've seen in recent years, it's possible that T-Mobile could do a lot with Sprint if it led the company. But many of the underlying issues — such as what happens to competition in a world of three national providers — remain.

As recently as last week, staff members at the Justice Department were said to be skeptical of a Sprint/T-Mobile deal. One argument you can expect to hear, analysts say, is that building out the next generation of wireless data — known as "5G” — will be fairly expensive and that it would be cheaper for everyone involved if T-Mobile and Sprint could join forces and build a single 5G network rather than build two of them separately. Another argument you might hear is that Sprint, whose business is weakening, simply can't survive alone and that by teaming up with T-Mobile, the combined company could more effectively compete with AT&T and Verizon.