It's too early to tell how or if yesterday's assassination attempt on former President Donald Trump will affect the November presidential election and that there are other factors that will help determine the outcome.

That's according to Edward Segal, a former campaign manager and aide to congressional candidates, a presidential campaign historian, and a crisis management expert. He's the author of  "Whistle-Stop Politics: Campaign Trains and the Reporters Who Covered Them" and "Crisis Ahead: 101 Ways to Prepare for and Bounce Back from Disasters, Scandals, and Other Emergencies."

"The attempt on Trump's life has created empathy and sympathy for the Republican presidential candidate in many quarters and strengthened the resolve of his supporters to send him back to the White House. But for entrenched supporters of President Joe Biden and independent voters who are more concerned about pocketbook and other pressing issues, it's doubtful that empathy and sympathy alone will be enough to convince them to vote for Trump," Segal said.

He noted that "another factor to consider will be the impact of calls from the leaders of both political parties to cool down the heated rhetoric that has been the hallmark of year's election season. If the temperature is lowered far enough and quickly enough, perhaps the candidates and voters will concentrate exclusively on policies and not focus on personalities."

"Elections can be like riding a new roller coaster for the first time, with unexpected and nerve-wracking ups and downs. Just because a candidate is up today, does not mean he or she won't be down tomorrow," Segal observed.

"We are months away from casting ballots, and there's no telling what other surprises may be in store on the presidential campaign trail between now and then," he commented.

Segal recalled that in 1912, there was an assasination attempt on former president Theodore Roosevelt as he sought re-election to the White House as the nominee of the Progressive Party. Roosevelt refused medical treatment, delivered a lengthy previously scheduled speech, and fully recovered from his wounds. The former Republican lost the race to Democratic presidential nominee Woodrow Wilson.

Threats Against Whistle-Stopping Politicians

In his book, "Whistle-Stop Politics," Segal documents politicians who faced threats while campaigning or traveling by train, including Abraham Lincoln in 1861, President Herbert Hoover in 1932 and Vice President Richard Nixon in 1960. 

Abraham Lincoln's whistle-stop train tour from Springfield, Illinois to his inauguration in Washington, DC in 1861 was marked by several threats to the president-elect's life.

For example, after his train left Cincinnati, Ohio, a bomb was discovered in a small carpet bag on a seat in the railroad car that was occupied by Lincoln and his family and friends. The bomb was found only because luggage was prohibited in the car.

The explosive device, which was timed to detonate in fifteen minutes, was quickly deactivated. It "would have exploded with a force sufficient to have demolished the car and destroyed the lives of all persons in it," according to a story by "The World" newspaper in 1861.