Some 6,000 conservative activists will begin arriving in Washington on Wednesday to kick off this year’s Conservative Political Action Conference, or CPAC, on Thursday morning at the Omni Shoreham. It will be the 35th such gathering, which began back in 1973 with about a hundred conservatives and Ronald Reagan, who ended up appearing at some 17 CPACs as governor, private citizen and, eventually, president of the United States.

In fact, upon winning the presidency, the 1981 CPAC was one of the Gipper’s first appearances following his inauguration. He told the crowd that year that some of his advisers had asked him, “Why CPAC?” His response was simple enough: “I told ’em I was coming here to be with you tonight because I am one who believes in dancing with who brung me.”

This year’s conference attendees will hear from President George W. Bush, Vice President Dick Cheney (who attends every year) and the still-standing Republican presidential candidates. The Democratic candidates are invited, but in the last couple of cycles none have bothered to answer the invitation, let alone show up.

Last year, Arizona Sen. John McCain, who enjoys what one might most accurately describe as an edgy relationship with the conservative activist community, blew off the conference as unimportant. This year he’ll join Mitt Romney, Mike Huckabee and Ron Paul, among others,  to address the men and women so important to any serious conservative seeking public office. McCain may or may not wow the crowd, and he may not leave the hotel as their favorite, but he and his handlers know that the folks who attend these conferences represent literally millions of conservative activists who can either help you get to the dance … or not.

Political pundits these days can’t decide whether to write off the conservative movement as passé or irrelevant or to ruminate over the question of whether a candidate like John McCain can win the presidency even if nominated without united conservative support. The same debate raged in the days leading up to the 2006 congressional elections.

Conservative outrage over out-of-control federal spending was ignored by Republican leaders at both ends of Pennsylvania Avenue who just didn’t seem to care much about the fiscal, philosophical or moral values so important to conservatives. Even after the elections, many analysts insisted it was independents and moderates rather than conservative discontent that had doomed Republican candidates. This debate took place mostly among Republicans, of course, who knew that they couldn’t be at fault. Democrats, for their part, simply took hot-button conservative issues off the table and ran candidates who identified not with the traditional Democratic positions of Speaker-to-be Nancy Pelosi (Calif.), but with those of Republican voters.

When it was all over, establishment GOP analysts argued that since most self-identified conservatives turned out and voted for Republican candidates, Republicans didn’t need to worry about the base. Oh, they acknowledged, the conservative turnout had dropped a little, but certainly not by more than 4 or 5 percent. That might not have mattered much to the analysts, but it meant a great deal to the Republicans and Democrats who won and lost races by 2 or 3 percent around the country.

The fact is that in an electorate as evenly divided on party and ideological grounds as is the American electorate circa 2008, every vote counts and no candidate can afford to go into a presidential race without knowing that his or her base is secure.

The millions of voters who just don’t like their party’s nominee aren’t going to stay home, but if a few do and a few more don’t work as hard as they have in the past or contribute as much as expected, their party’s nominee will enter the general election campaign with one hand tied behind his or her back. This is a fact that John McCain and Hillary Clinton have to worry about if they, in fact, think they are going to win their parties’ nominations.