Campaign comments and federal finger-pointing at Russia over email hacking raise concerns about foreign meddling in next month's presidential voting process. Worries arise after the July release of nearly 20,000 hacked Democratic National Committee emails and reports of a new cyberattack against the Democratic Congressional Campaign Committee. U.S. intelligence agencies believe the Russian government of Vladimir Putin is behind the summer theft, supposedly because Moscow leaders think a Donald Trump would be more favorable to their interests than Hillary Clinton.

But U.S. officials play down any threat to the integrity of Nov. 8 balloting, at least at the national level. The voting process remains "very, very hard to hack into because it is so clunky and dispersed," FBI Director James Comey told a U.S. House hearing last month. "It is Mary and Fred putting a machine under the basketball hoop at the gym. These things are not connected to the Internet." Still, he says, federal authorities urge state officials to secure voter registration databases and other systems being scanned by hackers for weak spots. Nearly 80 percent of U.S. voters will use paper ballots or machines with paper backups, both of which are considered much more secure than online-only systems.

For his part, Trump claims a possible threat could come from his opponent's side. At rallies and online, the Republican nominee invites backers to volunteer as polling place observers "to help me stop 'crooked Hillary' from rigging this election." In Pennsylvania this month, he told a rally: "We have to make sure that this election is not stolen from us." And at the final debate last week, he declined to say he'd accept the Nov. 8 outcome as valid. "Millions of people are registered to vote that shouldn’t be registered to vote," he replied to a question from moderator Chris Wallace.

That's risky rhetoric, says a California political scientist who warns against "sowing the seeds of distrust." The professor, Melinda Jackson of San Jose State University, fears that creating doubt about the election's integrity "puts us in a whole different category of countries that don't have free and fair elections." If Trump or a group supporting him questions the legitimacy of the outcome, Jackson adds, "we might see violence, we might see protests, we might see rioting -- things that we see in other countries. It's not impossible."

Hillary Clinton says: "We have never in the history of our country been in a situation where an adversary, a foreign power, is working so hard to influence the outcome of the election." – Reply during Oct. 9 debate

Donald Trump says: "I'm afraid the election's going to be rigged. I have to be honest." – At August rally in Colubus, Ohio

Journalist says: "Hackers don't need to actually hijack a voting machine or ballot software to undermine confidence in election results. Merely the credible claim that an election had been tinkered with could compel a candidate’s supporters to cry foul, particularly if the vote counts are close." – Shane Harris, The Daily Beast online news site