Top lawmakers on the Senate Intelligence Committee tell Axios their biggest fear in the immediate days after Tuesday's election is a "perception hack" that throws the country into a constitutional crisis.Why it matters: Networks of disinformation, both foreign and domestic, will have a long runway to undermine the integrity of our elections. Those aims could potentially be boosted if President Trump joins in on questioning the credibility of the system."This is a really dangerous moment; the only antidote is a landslide," Sen. Angus King (I-Maine) tells Axios.What we're hearing: The chief concern within the committee, top members say, is that America's foreign adversaries, namely Russia and Iran, will sow enough doubt in the credibility of the election that they will succeed in substantiating partisan claims that the election is fraudulent. "They don't have to change votes," King says. "They don't have to wipe registration rolls. All they have to do is raise doubt. All they have to do is raise enough questions so that those who are prepared to call the election fraudulent or unfair or rigged have some evidence upon which to make that claim."A senior Republican committee aide added that those doubts will likely come in the form of viral disinformation posts on Twitter and Facebook: "By the time we realize that it’s fake, it’s way too late. Half of our country will be locked into believing one thing, and half the country is locked into believing another, and then one side will think that the other party stole the election."This becomes an even bigger problem if the president himself amplifies these messages, lawmakers say. The committee's ranking Democrat, Sen. Mark Warner (D-Va.) tells Axios: "In recent months, the perception hack is coming from the White House by helping to spread disinformation about the integrity of the election. It’s a narrative foreign adversaries can leverage." Few Republicans were willing to go on the record before the election to say they're also extremely worried about Trump stoking these fears, but many privately acknowledged the president has put them in a tough position. "What do you do when the leader of your party is the person providing the fuel that could conceivably be used by foreign actors?" a GOP committee aide said.Acting Chair Marco Rubio (R-Fla.) said every American should "be cautious about believing or spreading unverified, sensational claims related to votes and voting."He says foreign adversaries may attempt "to stage fake voter intimidation, spread last minute sensationalist claims, or target our election systems and infrastructure — or simply leave the impression that they have altered or manipulated those systems.”The other side: “Election security has received more focus under President Trump than under any Administration before him,” a senior administration official told Axios.The bottom line, via Axios cyber security reporter Zach Dorfman: The disinformation campaign these foreign intelligence services will conceivably execute will be based on domestic schisms that they have watched percolate from the president."It's like basically just priming the pump for the disinformation campaign," Dorfman writes.To avoid falling into that trap, Warner says, Americans should "be smart" and "vote with confidence": "Don’t overreact to things you may see online that look questionable. We have a lot of smart people across both the federal and state governments working to combat misinformation; let them do their job."Go deeper: Trump plans to declare premature victory if he appears "ahead" on election night