MORGANTOWN, W.Va. -- With Election Day one month away, the United Mine Workers of America continues to sit out the presidential race for the first time in 40 years.

On Friday, the typically Democratic-supporting union announced it's backing Democrats in U.S. House and Senate races in 16 states, along with Republicans in two contests. But when the Coal Miners Political Action Committee, or COMPAC, met Thursday in Triangle, Va., it did not endorse either Democrat Barack Obama or Republican Mitt Romney.

No final decision has been made about whether either will eventually get a nod, said union spokesman Phil Smith.

On its website, the union says neither Obama nor Romney "has yet demonstrated that he will be on the side of UMWA members and their families as president. We will continue to examine the candidates' positions on all the issues of importance to our members and American working families as the campaign progresses."

The UMWA represents more than 100,000 members, including retirees. It backed Obama in 2008, but since then, the president's relationship with coal country voters has deteriorated, and he is now widely unpopular in states such as West Virginia.

Steve Jarding, a lecturer in public policy at Harvard University's John F. Kennedy School of Government and a former campaign adviser to Democrats in Virginia, said the lack of an endorsement isn't likely to hurt either candidate. Republicans aren't traditionally favored by unions, and most in coal country were not likely to vote for Obama anyway.

Several decades ago, unions represented a third of the private workforce, Jarding said, but that's dwindled to about 7 percent.

Most mines today are also non-union. The UMWA says it represents only about one-third of all active miners in the U.S., and more than two-thirds of its members are retirees.

While unions still have some power -- as evidenced by the recent teacher strike in Chicago -- Jarding said the loss of numbers means both the unions and their endorsements are "bound to have lost some clout."

"It still matters," he said, "but it isn't what it used to be."

What matters more is that many voters are convinced that Obama is waging a "war on coal" because his Environmental Protection Agency has tried to crack down on the permitting of mountaintop removal mines and imposed new water-quality rules only for Appalachian operations.

The EPA also set new air pollution standards for power plants, many of which were historically fired with coal. Old, inefficient plants have been going offline or converting to cheaper natural gas, dealing a blow to coal companies that had been supplying them.

The UMWA first endorsed a presidential candidate in 1936, with Franklin D. Roosevelt. Then it endorsed no one else until John F. Kennedy in 1960.

It hasn't sat out a presidential race since 1972, when its choices were Richard Nixon and George McGovern.

The union has, however, picked candidates in some other federal races this year. All are Democrats, with the exception of GOP candidates in congressional races in Alabama and Pennsylvania.

In West Virginia, it's backing incumbent U.S. Sen. Joe Manchin and Rep. Nick Rahall. It didn't choose a candidate in two other House races. In Ohio, Sherrod Brown gets the union's nod for Senate, along with eight House candidates.

In Virginia, the union is behind Senate candidate Tim Kaine, and House challengers John Douglas and Anthony Flaccavento.

Flaccavento is challenging Rep. H. Morgan Griffith, a first-term Republican in southwestern Virginia's "Fightin' Ninth" Congressional District -- the state's only coal-rich area.

Two years ago, Griffith unseated Democrat Rick Boucher, who had represented the district for 28 years, because of the perception that Boucher had acted against the interests of the coal industry. Griffith has been an outspoken supporter of coal but has opposed unions.

John Douglass is hoping to unseat first-term Republican Rep. Robert Hurt.

The West Virginia Coal Association has endorsed Romney's presidential campaign and is urging people to register to vote, saying there's never been an election "more vital to the future of our industry, our state and our nation."

"The major challenges and issues facing the industry today are political in nature being driven by political agendas that require political solutions," its website says. "Please make every effort possible to mobilize your friends and family to assist in getting out the vote."

In the West Virginia governor's race, however, the association is backing Democrat incumbent Gov. Earl Ray Tomblin.