Throughout his presidency, Barack Obama hasn’t exactly been a friend to marijuana users.

Sure, he has acknowledged smoking pot as a young man, but he has disappointed marijuana advocates by opposing its legalization, regulation and taxation like alcohol.

And the Justice Department’s occasional crackdown under his administration on medical marijuana dispensaries, which 17 states and the District of Columbia allow, has angered others.

So now, with Obama facing a stiff challenge from Republican Mitt Romney in the November 6 election, it’s ironic that his chances of winning the key state of Colorado could hinge on marijuana legalization, supported by a growing number of Americans.

At issue is whether Obama will get a boost from young voters expected to be among the most enthusiastic backers of a Colorado ballot initiative that would legalize possession of up to an ounce of pot for recreational use - and give the state the most liberal marijuana law in the nation.

The initiative is a reflection of Colorado’s unique blend of laid-back liberalism and anti-regulation conservatism that helped make the state the birthplace of the Libertarian Party.

It’s a state where people of different political stripes see marijuana laws as an example of government needlessly sticking its nose where it doesn’t belong.

It’s also a proving ground for advocates who see legalization as a way to ease crowding in prisons, generate much-needed tax revenues, create jobs and weaken Mexican cartels that thrive on Americans’ appetite for illegal drugs.

The Rocky Mountain State already allows the use of marijuana for medical purposes such as severe pain relief, and some communities have embraced it enthusiastically.

The prevalence of medical marijuana dispensaries in Denver has moved pot into the mainstream in Colorado’s capital city.

In Denver County, home to about 600,000 people, one in every 41 residents is a registered medical marijuana patient, leading to chuckles about the “Mile High City.” Denver is roughly a mile above sea level.

The number of places licensed to sell medical marijuana products has reached 400 here, according to the Denver Post. That means there are more dispensaries in the capital than there are Starbucks coffee shops (375) statewide.

A similar bill is on the ballot in Washington, another state that already allows use of medical marijuana. If approved, the initiatives would put the states squarely in the crosshairs of federal law, which classifies cannabis as an illegal narcotic.

PATH TO THE WHITE HOUSE

It’s unclear precisely how the U.S. Justice Department - whether led by Obama or Romney - would respond if Colorado, Washington or other states legalize marijuana for recreational use. Both politicians oppose legalizing the drug.

But in a close presidential election in which Colorado could be a tipping point - and with polls showing Obama has up to a 30-point edge over Romney among voters age 30 and under - the state’s marijuana initiative could be a factor if it inspires waves of young voters to cast ballots on November 6.

“This is an issue that is really meaningful to young people, people of color, disenfranchised communities,” groups that typically lag in registering and showing up to vote, said Brian Vicente, 35, executive director of Sensible Colorado, a group seeking less restrictive marijuana laws.

“Democrats and Obama need these groups to win,” Vicente said. “The path to the White House leads through Colorado. We feel we can motivate these groups.”

Last winter, Public Policy Polling found that 49 percent of Coloradans favored legalization, while 41 percent opposed it.

As much as some Democrats feel they have the wind at their backs, they are fighting history in Colorado. Obama won the state in 2008, but he was the first Democratic presidential contender to do so in 16 years.

And even though a majority of the delegates at the Colorado Democratic Party’s convention last month said they supported legalization, some party officials are skeptical the politically diverse movement will help Obama much this fall.