(Corrects this Oct. 5 story’s headline to conform with quote from professor that a Trump defeat would upset the verdict of history.)

Slideshow ( 8 images )

(Reuters) - The forces influencing the U.S. presidential election favor Republican nominee Donald Trump to win the popular vote - but even proven prediction models face “the most difficult election by far to predict accurately,” a political forecaster with a three-decade winning streak said on Wednesday.

History Professor Allan Lichtman of American University in Washington has accurately predicted the popular result in presidential elections since Republican President Ronald Reagan defeated Democratic challenger Walter Mondale in 1984.

Although the number of ballots cast by voters for each candidate counts, it does not ultimately determine who takes the White House. In a process known as the Electoral College, the candidate who wins a majority of 538 electoral votes is the victor. Each state and the District of Columbia is allocated a certain number of those votes, and the candidates have to amass them state-by-state on Election Day.

While Lichtman’s “Keys to the White House” analysis predicts a popular victory by Trump, some other models, such as FiveThirtyEight’s and The New York Times’, have given Democratic rival Hillary Clinton a large probability of victory.

Lichtman joined Reuters Global Markets Forum to discuss his take on Campaign 2016. What follows are excerpts from that conversation.

Question: Why is Trump your favorite to win?

Answer: With respect to my prediction, my “Keys” system is based on 13 true/false questions where an answer of “true” favors re-election of the White House party - the Democrats. They have exactly six “false” keys against them, just enough to predict their defeat.

However, I also noted that Donald Trump is such a dangerously precedent-breaking candidate that he could upset the verdict of history and snatch defeat from the jaws of victory.

The two candidates have been repeatedly fact-checked by independent sources, and his lies vastly outnumber hers.

Q: How big is the immigration issue in deciding the election?

A: I think immigration is a very important issue. America is a nation of immigrants and immigrants have been demeaned for more than two centuries, the French, the Irish, the Jews, the Asians, the Mexicans, and now the Muslims. The two candidates have fundamentally different approaches to dealing with the issue.

Q: What is your expectation for the next two debates?

A: Trump has got to convince voters that he has the temperament, knowledge, and background to be a dependable and effective leader. He can try to do that without losing his base, which will never abandon him.

The first debate was definitely a lost opportunity (for Trump), which may be hard to regain for him. Obama lost the first debate (against Mitt Romney) in 2012, but voters still did not have as many doubts about him as they do about Trump. In terms of temperament, he could take a lesson from Pence, but Trump has a great deal of difficulty preparing for a debate or keeping himself under control.