WASHINGTON — President Vladimir V. Putin of Russia dismisses the idea that he has the power to interfere with Tuesday’s election. “Does anyone seriously think that Russia can affect the choice of the American people?” he asked during a foreign policy conference last week in the resort city of Sochi. “What, is America a banana republic? America’s a great power. Correct me if I’m wrong.”

America’s top intelligence officials say he is highly unlikely to be able to alter the results. But they expect Russian hackers, or others, to try to disrupt the process — perhaps to help Donald J. Trump, but more likely to simply undercut what Mr. Putin views as America’s holier-than-thou attitudes about its democratic procedures.

The Obama administration has concluded that much of the email hacking that has roiled the campaign was almost certainly approved by the Russian leadership. More recent activity — including the probing of registration rolls in several states — might be the work of independent Russian hackers, it says. While no one knows what to expect before the polls close, a tight race is more susceptible to mischief.

So government agencies and commercial enterprises, including some hired by state election boards facing a determined cyberthreat for the first time, are on high alert. But they are not exactly sure what to look for. Russian hackers? Other attackers? Malware that harnesses devices to strike election infrastructure? More email revelations?