About 6.5 million Hispanic voters will likely cast their ballots this year, according to the National Association of Latino Elected and Appointed Officials - nearly 1 million more than in the last midterm elections in 2006. The group derived its estimate by looking at the increase in Hispanic voter turnout in the past three congressional elections.

The voting bloc could have an impact in close races from Texas to Colorado, said Arturo Vargas, executive director of the group.

"Never before have we had so many tight contests at the state and federal levels in states where the Latino vote can make a difference," he said. "I think it will make all the difference in 2010."

Vargas's group says that several elections could turn on the Latino vote, notably gubernatorial contests in California, Colorado, Florida, Nevada, New Mexico and Texas. Some of the Republican nominees are Hispanic: Brian Sandoval in Nevada and Susana Martinez in New Mexico.

Recent studies have shown a lack of enthusiasm among Hispanics for the upcoming election. The Pew Hispanic Center earlier this month found that about one in three Hispanic voters had given "quite a lot of thought" to the November election, compared with 50 percent of all registered voters. A Post-Kaiser-Harvard poll this month found that about 35 percent of Hispanics were "very interested" in their upcoming congressional races, a smaller proportion than other demographic groups.

But Vargas said his observations contradict the contention that Latinos are less energized. He said some groups, however, are bent on making those predictions come true.

In particular, he criticized a recent campaign mounted by a conservative group discouraging Hispanics in Nevada from voting this year. The group, Latinos for Reform, has placed television ads suggesting that Democratic leaders have wronged the community by failing to follow through on their promise to pass comprehensive immigration reform. The Spanish-language ad says bluntly, "Don't vote."