By March 2006, trailing Green in polls and with only about $500,000 in his campaign account — roughly a quarter of what his opponent had — Walker decided to withdraw. The writing was on the wall: At a state Republican Party dinner that Green and Walker attended earlier in the month, Vice President Dick Cheney acknowledged Green from the podium but made no mention of Walker. The omission left some wondering if the Bush White House, eager to circumvent a primary, was trying to push him out of the race.

The evening Walker made his announcement, he appeared side by side with his opponent at a political event in Waukesha, promising his “full support and endorsement.” The two embraced.

Many Walker allies look back on the day as a pivotal moment. Prior to the announcement, Walker and his advisers pondered launching a no-holds-barred offensive against Green. Instead, they settled on a different course, based on a cold-eyed assessment of the landscape.

By wholeheartedly getting behind the front-runner and crisscrossing the state on his behalf, Walker could build party goodwill, not to mention preserve his viability as a future candidate. With 2006 shaping up to be a disastrous year for Republicans and Green likely to be the underdog in the general election, Walker’s thinking went, he could endear himself to party activists and position himself for a 2010 campaign, when the political environment could be more favorable.