BEWARE of habitual monopolists bearing gifts—especially if they operate in shamefully uncompetitive markets. AT&T's proposed $39 billion takeover of T-Mobile USA would create a dominant mobile-phone operator, with a 39% market share in America, and a near-duopoly with Verizon, the current market leader: together their combined share would be 70%. It is a mark of the mess that the United States has made of telecoms not just that such a deal is being considered, but also that a duopoly might actually bring genuine short-term benefits. All the same, it would be far better if the Federal Communications Commission (FCC) and the Department of Justice blocked the T-Mobile merger—and tried to reform the market instead.

The bait for Barack Obama is that the deal could speed up his commitment to make broadband available to more Americans. AT&T says the acquisition will let it expand its fourth-generation (4G) technology—which will provide faster data connections on mobile devices—to a further 46.5m Americans, including many in rural areas who cannot get fixed-line broadband. This is much the same argument that AT&T's grandmother, Ma Bell, made a century ago when it lobbied successfully to be allowed to swallow up lots of other telephone operators and become a monopoly, on the ground that this was the best way to ensure decent coverage, especially in a huge country with a thinly spread population. In the 1970s the government decided that technological gains had undermined such “natural monopoly” arguments: AT&T's local phone services were subsequently hived off, and it was forced to accept competition for long-distance services.

Why reverse history? AT&T argues that by making better use of the two firms' combined infrastructure it could improve the quality of connections. It says the merger, by making it a stronger rival to Verizon, would improve the industry's competitiveness. Consumers everywhere would have a choice between two strong national companies.

This new-found zeal for serving consumers needs to be taken with a pinch of salt: AT&T now gets the worst customer-satisfaction ratings among the main mobile operators. The deeper question is whether two is enough, especially in a business that is evolving as fast, and becoming as important to people's lives, as mobile communications. Canada—also vast and sparsely populated—concluded that lack of competition had contributed to its having some of the rich world's most expensive call rates, and has been trying for three years to promote new entrants. The FCC's British counterpart wants to manage its 4G auction to guarantee consumers have at least four operators with nationwide coverage.

AT&T points out that consumers in many American metropolises already have a choice of five or more operators; and it is prepared to give up market share in some localities where the merger would make it dominant (see article). But many consumers want a mobile operator with good national coverage. That is why AT&T and Verizon each spend so heavily on advertisements claiming they are the best for this.

The president's call

The suspicion is that Mr Obama, desperate both to build some broken fences with big business and to make progress on connecting every American home to the internet, will give in. In fact he should push the FCC to promote more competition—by, for instance, allowing other firms to buy bulk wireless capacity from AT&T and resell it, by freeing up underused spectrum and by making local phone and cable firms share their wires. A duopoly would in the end reduce choice for American consumers, and be hard to reverse. Best to block it.