When the people of Taiwan vote in presidential and legislative elections next month, nobody will be more intensely interested in the outcome than Beijing and Washington.

Reason: Whoever is elected will most likely exert strong influence on the course of Taiwan’s relations with mainland China for the foreseeable future. If those relations are not handled well, that could cause a dangerous confrontation that could, in turn, lead to hostilities between the United States and China.

Up for reelection is the incumbent president, Ma Ying-jeou of the Nationalist Party or Kuomintang, who asserts he would continue his three-year effort to ease tensions across the Taiwan Strait between the mainland and his self-governing island.

The main challenger, Tsai Ing-wen, chairwoman of the Democratic Progressive Party, promises to continue some of President Ma’s approaches to Beijing but would insist on asserting Taiwan’s sovereignty and separation from China.

A third candidate, James Soong of the People First Party, has no chance of winning but will take unknown numbers of votes from the other two candidates, making the result unpredictable.

“This whole thing is too close to call,” said an experienced American diplomat. He and others were skeptical of the accuracy of the polls, most of which show President Ma slightly ahead.

The communist government in Beijing has long asserted that Taiwan is a part of China and that island of 23 million people must be returned. Otherwise, China may resort to military force to achieve that.

The U.S. has asserted that the future of Taiwan must have the consent of the people there and must be peaceable. The Taiwan Relations Act of 1979 may require the use of U.S. military force to prevent conquest by China.

Beijing has let it be known that it favors President Ma even though he comes from the Kuomintang, their ancient foe. Ma is seen as being more receptive to Beijing’s position on economic issues and not opposed to Taiwan’s eventual unification with the mainland.

From Washington’s point of view, President Ma is to be applauded for cooling tempers in cross-strait relations. On the other hand, he has done little to improve Taiwan’s ability to defend itself. Military spending, for instance, has hovered just above 2 percent of gross national product rather than the 3 percent he pledged before taking office.

In contrast, Ms. Tsai is held suspect by Beijing because her party advocates Taiwan’s independence. She is considered more moderate on that issue, however, than former President Chen Shui-bian of the DPP, who served from 2000 to 2008. Said a Tsai supporter in Taipei: “She sees no need to be confrontational.”

If elected, Ms. Tsai would seek to strengthen Taiwan’s military forces to hold off Chinese invaders long enough for the U.S. to come into the fight. She would also seek to improve military ties with U.S. forces, particularly the Pacific Command with its headquarters in Hawaii.

Obama officials have taken no public position, as is usual on other people’s elections. Privately, they suggested that President Ma was known and they foresaw no surprises. They pointed out, however, that Ms. Tsai had been engaged in cross-strait relations as chair of the Mainland Affairs Council, a main channel of communication with Beijing.

The Associated Press reported from Taipei that the campaign had been relatively low key until a televised debate a week ago. President Ma sought to link Ms. Tsai to former President Chen who has been convicted of corruption and is in prison.

Tsai retorted that she was running in 2012, not 2008, and accused Ma of opening the door for China to bring Taiwan under its sway. Instead, she portrayed herself as a centrist who would unify the people of Taiwan to deal with China.

Whatever the outcome, it seems fair to conclude that this campaign has nourished the roots of Taiwan’s democracy. The election of President Lee Teng-hui of the Kuomintang in 1996 marked the first direct presidential election in the history of the Chinese-speaking peoples. The 2012 vote, on Jan. 14, will be the fifth such election.

Some 66 percent of Taiwan’s voters are expected to cast ballots, compared with 58.5 percent in 2008 and 76 percent in 1996. In the U.S., 58 percent of the voters turned out in 2008.

In addition, press reports from Taipei say that last week’s campaign debate was carried by television and the internet to China. The result of the voting is also expected to be carried on mainland TV and internet. In the past, the Chinese government, which does not care for displays of democracy, has often banned such reports.