The prospect that Barack Obama will face labor troubles at the Democratic National Convention in Denver this August is increasing.

The potential for labor strife at Denver’s convention has been in the air since the Democratic National Committee selected it as the host site for the convention. Although convention organizers have worked through the problem of the DNC’s venue not being unionized — the Pepsi Center will use union workers for the event — two major problems loom:

First, school teachers in Denver are militating for a new contract; the current one will terminate the Sunday following the convention. The local paper, The Denver Post, which ran a story with the sub-headline “A Teachers Contract Dispute Could Erupt During the Convention,” is calling attention to the potential for chaos. According to the Post, the school administration and teachers are squabbling about teachers’ compensation.

Second, after decades of tranquility on the labor front, between now and November Colorado is the scene of a the contentious statewide battle between the “Right to Work” initiative, backed by the business community, and several other initiatives supported by labor, drawn up in response to the measure.

A professor at Colorado College and the author of “Colorado Politics and Government,” Robert Loevy, describes his state’s citizens as being “on edge” regarding these labor issues. “A controversial Right to Work initiative that’s qualified for the ballot. That campaign will be starting up. A potential school strike and coming in the middle of all this, the Democratic convention,” he says. “It’s interesting to me that these various labor issues are playing so strongly exactly when the political party most associated with labor is bringing their political convention to town.”

The labor troubles in Denver in August may be Mr. Obama’s biggest test since besting Senator Clinton earlier this month. As is customary for the Democratic nominee, Mr. Obama will need strong support of organized labor in his presidential run. Labor unions are an important source of money and manpower in general election fights. Still, a sticky union fight could be embarrassing for Democrats who want to present a unified face at convention time.

Unfortunately for Mr. Obama, both topics will be hard to avoid. Last November, speaking in Manchester, N.H., at the formal announcement of his education plan, Mr. Obama singled out for praise the very same Denver school system that is now quarreling over teachers’ compensation when talking about his own education plans, which include a form of “merit pay.”

He specifically cited the example of Denver’s school system in proposing that teachers be compensated for the quality of their work. “Cities like Denver have already proven that by working with teachers, working with teachers — not doing things to teachers — this can work, that we can find ways to increase pay that are developed with teachers, not imposed on them and not just based on an arbitrary test score,” Mr. Obama said. “Where our teachers go above and beyond the call to make a real difference in our children’s lives, I think it’s time we rewarded them for it.”

But according to the Post, the teachers in Denver aren’t interested in merit pay — they want across the board raises. That Mr. Obama has already opened himself up for discussion on the subject of Denver’s school teachers will make it more difficult for him to duck the issue when he arrives for the convention in August.

Even if Mr. Obama is somehow able to quietly avoid the teachers’ dispute in Denver, there is still the battle over the “Right to Work” initiative, which is better known as Amendment 47, that will be on the ballot in November. For decades, the so-called Labor Peace Act has governed labor relations in Colorado. A series of developments — including Democrats taking control of both branches of the state Legislature and the governor’s office, and the governor’s signing of an executive order in November 2007 permitting state workers to unionize — prompted business leaders to push for a measure that would make it possible for union and non-union workers to be employed at the same establishment.

“The Democrats are trying to push Colorado to a more anti-business condition and we’re fighting back in reaction,” Kelley Harp, a spokesman for “A Better Colorado,” the issue committee backing Amendment 47, said.

Union leaders view the act as divisive and hurtful to workers, and as a result, the United Food and Commercial Workers Local 7 has sponsored several of the counter-measures to Amendment 47. The union endorsed Mr. Obama in February and sent volunteers to Texas to work on his behalf, which will make it difficult for Mr. Obama to avoid being drawn into the fray in Denver. UFCW Local 7’s counter-measures are pushing rules mandating health insurance at companies with more than 20 employees, ending the limitation of workers injured on-the-job to workers compensation, and banning the state from providing tax credit to employers who have offshore operations. The deadline for the signatures on these proposals is in August, only weeks before the convention.

It’s possible that Mr. Obama will escape the prickly prospect of having to take a direct stand on these labor issues. The teachers could come to some resolution with Denver’s school leaders. The UFCW Local 7, which has already abandoned two other labor questions, could fail to get the requisite number of signatures needed to have their initiatives on the ballot or shelve the others in a goodwill gesture. But the spokesman for Amendment 47, Mr. Harp, says his measure will be voted on in November no matter what happens with other initiatives.

This leaves Mr. Obama in a quandary. The convention is typically the time when a candidate puts forth his best effort to capture America’s center-leaning voters. A full-blown display of opposition to Amendment 47 by Mr. Obama could put him too far to the left when he needs to be moving to the middle. A failure to speak in favor of Colorado’s workers, on the other hand, could further stoke his problems with blue collar Americans. During Mr. Obama’s unique presidential run, a tremendous amount of goodwill has rendered him immune from attacks rooted in specifics. Labor troubles in Denver have the potential to demonstrate whether that immunity can survive.

Mr. Gitell (gitell.com) is a contributing editor of The New York Sun.