LAS VEGAS — Volunteers for President Obama have flooded into Latino-owned nail salons here, buttonholing potential Obama voters as they sit captive in their chairs. In Colorado, supporters of Mitt Romney are recruiting Latino owners of small businesses to reach out to other business owners whom they view as particularly receptive to the Republican economic message.

Mr. Obama and his supporters have outspent Mr. Romney and his backers nearly 2-to-1 on advertising on Spanish-language television stations in three of the most closely contested states — Colorado, Florida and Nevada — including a new advertisement in which Mr. Obama makes a personal appeal for support, speaking entirely in Spanish. Mr. Romney’s advisers have relied on a surge of ads across the television spectrum, saying that most Hispanics speak English and consider the economy, not immigration, the top issue.

But if their strategies differ, both campaigns have determined that turning out Latinos in those three states is potentially critical. Mr. Obama is trying to roll up an outsize margin among Hispanics that could edge him to victory in those states, while Mr. Romney is seeking to hold down the president’s numbers.