Memo to George W. Bush: tread lightly, or you may rouse a bull moose that will stampede Republican dreams of capturing the White House. Arizona senator John McCain is stirring the political pot in a way reminiscent of his personal hero, Teddy Roosevelt. Sen. McCain's message is similar to that of the Rough Rider of San Juan Hill: we need a tough, independent leader to change the way business is done in Washington. As president from 1901 to 1909, Roosevelt was an energetic reformer, busting up monopolies and pursuing an aggressive foreign policy. That certainly sounds like McCain's vision of his presidency. The smart money in Washington, however, remains on George Bush to win the Republican nomination. McCain may have the crowds and the enthusiasm, but Bush has money -- lots of it -- and, more importantly, the full weight of the Republican establishment on his side. McCain's recent announcement of a unilateral halt of negative ads should give Bush loyalists pause, however -- not because of the likely effectiveness of the strategy, but because of its possible implications. Voters may dislike negative ads, but they are quite effective in winner-take-all elections. Pulling such ads thus is almost certainly bad short-term politics, but it could win favor with independents and Democrats in a general election. Bush must be careful lest he find himself in a similar quandary to Republican president William Howard Taft in 1912. That year, Teddy Roosevelt sought the nomination against Taft. Despite Roosevelt having the people on his side, the party bosses stayed with Taft. Furious, Roosevelt mounted the 20th century's greatest challenge to the two-party system. The Progressive "Bull Moose" party nominated Roosevelt for president and ran candidates for congressional seats across the country. Roosevelt beat Taft, but the Republican vote was so badly split that Democrats won the presidency and both houses of Congress. Bush may well be able to win the Republican nomination fair and square. In that case, McCain will likely accept defeat. But if the Bush campaign resorts to attack politics and insider power grabs, McCain just may decide to follow Roosevelt's example. This year, the nomination of the Reform Party and 13 million dollars in matching funds is ripe for the picking. Pat Buchanan has the inside track, but if McCain jumps -- or is pushed -- from the Republican ship, the nomination is surely his. Although the party is badly split, backers of both major factions have made overtures to McCain. McCain already has stated his willingness to accept a dual nomination from both Republicans and Reform. McCain has time to decide. The Reform nomination will be decided in a national mail-in ballot this summer open to any American citizen. Candidates for the nomination need only gain ballot status in some 20 states before the balloting -- not easy, given most states' byzantine ballot access laws, but certainly achievable for a candidate with McCain's momentum. McCain could be an extremely strong candidate in a three-way race in November, particularly if the major parties nominate the familiar names of George Bush and Al Gore. Minnesota Reform Party governor Jesse Ventura beat out similarly well- known fixtures of his state's politics in 1998. The quiet secret of modern politics is that Americans are tired of the two-party system. For example: A December 1999 poll by Harvard's Vanishing Voter Project found that only 23% of Americans agree that "the two-party system works fairly well." About half wanted to consider a third party candidate no matter who won the major party nominations. A January 2000 poll by Rasmussen Research found that if a third party candidate had a legitimate chance of winning a congressional race, 30% of likely voters would vote Democrat, 25% Republican and 26% for the third party. If McCain believes his reputation is being sullied and Republican doors are unfairly locked, he just might accept the embrace of Americans ready for an independent bid. Ironically, George Bush, the epitome of the Republican status quo, would have launched a new "rough rider"-- one who either smashes the increasingly sluggish two-party system with a victory or so divides the Republican vote that a Democrat waltzes into the White House for another four years.