One presidential candidate officially stepped into the race this week, while another, mercifully, stepped out. Sen. John McCain of Arizona announced his candidacy for president in Nashua, N.H. McCain pledged to lower taxes, pass more rigorous campaign finance controls and increase military spending, but also made numerous references to his military experiences and knowledge of foreign policy. The speech was a good start that will require much more detail as the campaign proceeds.

In an unsubtle dig at his chief competitor, George W. Bush, and the present occupant of the office, Bill Clinton, the senator noted that there were critical moments when the president “can no longer rely on briefing books and talking points. When a president makes life and death decisions he should draw strength and wisdom from the broad and deep experience with the reasons for and the risks of committing our children to our defense,” he said. “For no matter how many others are involved in the decision, the president is a lonely man in a dark room when the casualty reports come in. I am not afraid of that burden. I know both the blessing and the price of freedom.”

The candidacy of Sen. McCain — combat veteran, son and grandson of Navy officers — promises to underline the role of character and achievement in the race for the Republican nomination. His rivals, Gov. Bush and Steve Forbes, come from wealthy families, obtained exclusive educations and have lived lives of comfort and privilege.

The senator’s strategy might be to point out that there were times in his life when he could have taken advantage of familial connections but chose a truer, more difficult course.

His candidacy places Republicans exactly where they should want to be in preparation for the general election. They will be forced to answer how much character counts in electing a president. The answer may seem obvious, but it is not. Will voters prefer Gov. Bush, a man of charming personality whose “compassionate conservatism” holds the promise of widening the Republican Party tent but may have Clintonesque tendencies, or Sen. McCain, whose character was remade by the harsh adversity of torture in a North Vietnamese prison?

One candidate Republican voters won’t have to consider is former vice president Dan Quayle, who withdrew this week. An impressive young senator from Indiana prior to his nomination in 1988 by President George Bush, his repeated slips of the tongue became TV comedy fodder. Rather than return to his home in Indiana and run for elected office again after the Bush-Quayle ticket loss in 1992, he took a position as professor at a place called The Thunderbird School of Management in Phoenix, Ariz. The vice president was an early proponent of family values through a confusing confrontation with the fictional TV character Murphy Brown. His consistency on this issue brought him respect by conservatives and even a few moderate members of his party. But for many Republicans he remained an embarrassment, and Sen. Lloyd Bentsen’s slap in their vice presidential debate — “I knew Jack Kennedy,” etc. — may well be his political epitaph.

Sen. McCain offers an appealing conservative counterpoint in a race that once appeared over before it had begun. Win or lose, the senator should help his party rally voters, focus its message and choose its political direction.