Few headlines were written when, as the CEO of CBS, Mel Karmazin testified eight years ago before a Senate antitrust subcommittee regarding the network’s proposed acquisition by Viacom. If only he were so lucky today.

Mr. Karmazin is now CEO of Sirius Satellite Radio. Since the market closed on February 16, before Sirius’s merger with XM was announced, the value of XM stock has declined 3.5%; Sirius stock has slid nearly 10%. Meanwhile, broader market indexes such as the S&P 500 are down less than 2%. Something has gone wrong with the merger.

The financial fundamentals of the satellite television systems’ merger are sound. With high fixed costs and operational staffs but with limited subscriber bases, both XM and Sirius are bleeding money. Combine the two companies and eventually the cost structure will be closer to that of one company, while the revenue will be that of two. If the merger were merely for financial markets to decide, it would have been a winner. Shares of both companies rose in the days immediately after the announcement.

The challenge for XM and Sirius today is not the financial possibilities but the regulatory realities in Washington. Two entities, the Department of Justice and the Federal Communications Commission, will review the merger, and each presents formidable hurdles.

DOJ will decide whether the proposed merger would lead to such an increase in market power that the combined company would have the capability of raising prices. If the agency decides that satellite radio is a separate market, and the merger is a shift in industry structure from two firms to one, the merger likely will not be approved. If the agency decides, as the merging parties argue, that the relevant market is much broader, and includes a wide range of audio services in which the merging parties are not dominant, the merger may well be approved.

The FCC will determine whether transferring the FCC licenses is in the “public interest.” The agency will make a decision based on the public record as well as on the record of past compliance with commission rules.

When Viacom proposed to acquire CBS in 1999, Republicans controlled both houses of Congress, and there was little organized opposition to mergers of large press and broadcast companies. Congressional hearings were not designed to derail the merger, and serious negotiations took place at the DOJ and the FCC. Mr. Karmazin then spoke publicly about the merger and, while that may not have had any effect on the outcome, the merger was approved with few conditions.

Times have changed. Congress, now in Democratic hands, is much more skeptical of mergers generally and press and broadcast mergers in particular. Congressional hearings on mergers are not scheduled as pep rallies but rather as opportunities to weaken the deal based on statements from witnesses. Congress cannot insist that DOJ or the FCC reach any particular conclusion, but it can create a public record that, at best, reduces the flexibility a company has to negotiate terms and conditions with a merger-review agency. At worst, the public congressional record can humiliate the company.

Recognizing that regulators would pose the greatest obstacle to the merger, sensible management of XM and Sirius would have focused public statements regarding the merger on cost savings and not mentioned retail pricing. Public statements would be made by senior management, but not by CEOs who would attract television coverage as well as lack plausible deniability for any misstatements.

Congress has held three hearings in recent weeks on the proposed merger, and may hold more. Mr. Karmazin has testified at each hearing, and he has made new and evolving concessions about the merger — particularly with respect to rate plans. The substantial corporate attention given to retail pricing after the merger undermines many claims it could make to DOJ about the lack of capability to raise prices. Mr. Karmazin has also repudiated the suggestion that both companies could not survive independently.

Each congressional appearance by Mr. Karmazin has made government approval of the merger more difficult. The challenge remaining for XM and Sirius is to recover from poor management of the merger during the past month. Sometimes silence is a virtue.

A former FCC commissioner, Mr. Furchtgott-Roth is president of Furchtgott-Roth Economic Enterprises. He is organizing the seminar series at the Hudson Institute. He can be reached at hfr@furchtgott-roth.com.