"Many, many Republicans and Americans yearn for a new kind of leadership," said Warren Rudman, the former Republican senator from New Hampshire who is co-chairing the committee with Sen. Jon Kyl, R-Ariz.
"That's why we believe he must seriously consider running for president in 2000," Rudman added.
McCain, who has bucked his party's leadership on issues such as anti-tobacco legislation and campaign finance reform, has decided to run and is expected to announce his candidacy in the next several weeks, a senior adviser said Tuesday night, speaking on condition of anonymity.
Rudman said the formation of an exploratory committee would be announced today, marking "the first significant step forward in a campaign for president by John McCain."
McCain was on vacation and unavailable for comment.
Rudman said McCain has received "significant encouragement" to enter the 2000 contest from "a wide array of people over the last several months." He said many offered political or financial support to McCain if he runs.
Still, McCain was in the single digits in presidential preference polls taken earlier this year. One obstacle is that more than half of the people in a CNN/Gallup/USA Today poll taken in late spring had never heard of or had no opinion of him.
Kyl said "Arizonans, like many Americans who know him, are proud of John McCain both for what he has done and what he can do for the country."
Other expected contenders for the GOP presidential nomination include: George W. Bush, governor of Texas; Lamar Alexander, the former Tennessee governor and Education secretary who ran for president in 1996; Steve Forbes, the billionaire who lost the GOP presidential nomination in 1996; Sen. John Ashcroft of Missouri; and former vice president Dan Quayle.
McCain, 62 years old and father of seven, has served in the Senate since 1986. He was elected to the House in 1982.
Two of McCain's biggest legislative efforts in this Congress new curbs and taxes on tobacco and campaign finance reform both failed.
The Senate last summer killed McCain's $516 billion anti-smoking bill and its proposal to raise cigarette prices by $1.10 a pack.
In September, the campaign finance reform bill he and Sen. Russell Feingold, D-Wis., wrote together died. It would have banned unlimited and unregulated "soft money" donations to political parties, expanded disclosure requirements and regulated so-called issue ads that seek to influence elections under the guise of educating voters.
McCain spent more than 20 years in the Navy but it is the 5-1/2 years he spent as a prisoner of war in Vietnam that people remember.
He was 31 when his jet was shot down over Hanoi on Oct. 26, 1967. He broke both arms and shattered a soulder and a knee in the crash. Once on the ground, he was stabbed with a bayonet in the ankle and groin by a North Vietnamese mob. The injuries left McCain with a slight limp.
McCain once said that the two worst times in his life were his years in the Vietnam prison and the months surrounding the "Keating Five" scandal from 1989 through 1991.
McCain and four other senators ultimately were rebuked by the Senate Ethics Committee for intervening with federal savings and loan regulators on behalf of failed Arizona financier Charles H. Keating.
The ethics panel said McCain showed poor judgment in his efforts for Keating, who had been a major contributor to his campaign. McCain later turned over $112,000 in Keating campaign contributions to the Treasury.
Since 1997 McCain has been chairman of the Senate Commerce Committee, whose jurisdiction includes telecommunications, transportation, science and technology. He was one of five senators who voted against a historic overhaul of telecommunications laws in 1996.
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