A strong economy usually benefits incumbent presidents, but it isn’t always decisive and public perceptions of the nation’s trajectory are more important.

Barack Obama won re-election with Election Day unemployment at 7.7% and gross domestic product growth an anemic 0.5%. Lyndon Johnson withdrew his nomination in March 1968 with unemployment at 3.7% and GDP growing at 8.4% -- but with thousands of American men killed at the height of the Vietnam War.

George H.W. Bush was defeated in 1992 despite economic growth of 4% or better for four consecutive quarters. He suffered from perceptions he was disconnected from the public after a six-month recession in 1990-91, and the unemployment rate was still 7.4% on Election Day.

Trailing Rivals

At the moment, Trump trails six of his top Democratic rivals in hypothetical head-to-head match-ups, according to a Quinnipiac University poll released last week. He doesn’t exceed 42 percent of the vote against any of them, and loses by 13 points to former Vice President Joe Biden, the poll found.

Internal Trump campaign polling has also shown Biden leading Trump or within the margin of error in a number of key states for several months, according to a person familiar with the data. Trump has publicly insisted that all of his campaign’s internal polling shows him winning re-election.

“Looking at everything together right now, his prospects for another term are pretty dicey, though not inconceivable,” Abramowitz said.

Lichtman said he ignores national polls and looks instead at how Trump has performed while in office, examining factors including foreign policy successes, economic performance and midterm election performance. His model shows Trump with a comfortable cushion. That could change if House Democrats begin impeachment hearings, heightening the swirl of scandal around Trump, he added.

One problem is that Trump doesn’t get full credit for the economy, said Frank Luntz, a Republican pollster. While 70% of voters say the economy is excellent or good, only 41% say Trump deserves the credit, according to the Quinnipiac poll -- about the same percentage who say they’d vote for him over a Democrat.

And there is no guarantee that the economy will hold on its current course. Most private forecasters expect the economy to slow entering the election year, as growth cools overseas, trade disputes threaten global commerce and the fiscal stimulus from Trump’s deficit-financed 2018 tax cut fades.