AT&T Inc's agreement to acquire Time Warner Inc for $US85 billion (NZ$118.6 billion) has drawn scepticism from both Democrats and Republicans, making it more likely that regulators will scrutinise the effort to create a new telecommunications and media giant.
The deal, announced just two weeks before the US election, may be the strongest sign yet that corporate America expects Democrat Hillary Clinton to be the next president and maintain the same tenor as President Barack Obama on anti-trust and regulatory enforcement, which is seen as already tough.
Clinton spokesperson Brian Fallon told reporters on Sunday there were "a number of questions and concerns" about the deal "but there's still a lot of information that needs to come out before any conclusions should be reached".
Democratic vice presidential candidate Tim Kaine, Ms Clinton's running mate and a senator from Virginia, said lawmakers and regulators would have to review the deal and "get to the bottom" of questions over whether the merger would decrease competition.
Donald Trump said at a rally on Saturday that he would block it if he wins the election against Ms Clinton.
"It's too much concentration of power in the hands of too few," said Mr Trump, who has accused the media of being biased against him and his campaign.
The US Justice Department, not the president, has the power to reject such a deal if it violates antitrust laws. AT&T said it is unclear if the Federal Communications Commission will also have jurisdiction to review the deal.
A spokesperson for the Justice Department declined to comment on the deal on Sunday and an AT&T spokesperson also declined to comment on lawmaker criticism.
The biggest deal in the world this year will, if approved by regulators, give AT&T control of cable TV channels HBO and CNN, film studio Warner Bros and other coveted media assets. It raises concerns that AT&T might try to limit distribution of Time Warner material.
AT&T CEO Randall Stephenson told reporters on Saturday night he believes regulators will approve the deal.