“There is so much panic in the U.S. political establishment over Russia right now that Trump will be boxed in on what he can do,” said Matthew Rojansky, a Russia expert at the Wilson Center think tank in Washington.
White House officials say there were no improper contacts, and Russia denies any meddling.
While Trump has yet to lay down his Russia policy, most signs suggest no swift changes in the relationship, which sank to a post-Cold War low under his predecessor Barack Obama, mostly due to bitter differences over Syria and Ukraine.
Mattis sought to reassure NATO allies during a visit to Europe last month, telling them there would be no military cooperation between the United States and Russia in the near future.
U.S. Ambassador to the United Nations Nikki Haley this week denounced Russia for casting a veto to protect the Syrian government from Security Council action over accusations of chemical weapons use, and also recently insisted the United States would not recognize Russia’s seizure of Crimea.