Trump's path to the GOP nomination was cleared this week when the last of his Republican challengers, Sen. Ted Cruz and Ohio Gov. John Kasich, dropped out of the race.
Both he and Hillary Clinton, who is the frontrunner for the Democratic nomination with just four weeks to go in the US primary season, have pivoted to the general election -- and is customary in the US, they're already attacking each other.
In talking up coal, Trump is characterizing Clinton as a "job killer."
Coal has slumped in recent years for a number of reasons -- the biggest being the rise in environmental awareness and the resultant embrace of cleaner, healthier sources of power.
In 2008, about half the electricity generated in the US came from coal.
Today, it's place in the nation's energy mix has been cut substantially -- it's down to about one-third -- having been supplanted by renewables, nuclear power and especially natural gas.
The coal-energy industry has also been idling older plans in order to meet tighter clean energy standards.
As a result, US coal production was down about 10 percent in 2015, according to the US Department of Energy, and it is expected to drop another 16 percent this year.
Political analysts in the US admit they were taken by surprise by the anger and frustration of large white, rural voters in the US that has manifested itself in the presidential race.
And in coal country, the government, and its policy toward energy is seen as a source of the frustration.
In 2009, when President Obama took office, there were 84,600 coal-mining jobs in the US. In March, there were just 56,700, the US Labor Department said.
Making comparisons to the job growth that's occurred during the same period in the renewable energy sector is difficult because until 2012, the federal government lumped those statistics under one heading with the statistic from other sectors.
Now, solar, wind, geothermal and biomass all have their own classification under the North American Industry Classification System.
And that's the key to finding renewables employment data, according to Rick Wise of the US Bureau of Labor Statistics.
Armed with the classification data, Wise walked Renewable Energy Magazine through the agency's "Quarterly Census of Employment and Wages," a regularly compiled analysis that is reported with a six-month lag time. In other words, right now the most up-to-date statistics are from the third quarter 2015.
Looking at that data, private employment in the solar sector in the US went from 658 jobs in 2012 to 2,134 jobs as of September 2015.
Similarly, jobs in the wind sector climbed from 3,190 in 2012 to 4,310 in September 2015; in the biomass sector from 1,291 in 2012 to 1,569 in 2015; and in the geothermal sector from 1,053 to 1,094.
As for Trump and coal, the candidate has not said definitively what he would do to increase mining jobs in the US. An advisor has suggested the first order of business would be a review of Environmental Protection Agency regulations affecting the industry.