Al Sharpton (search), an asterisk in polls measuring support for the Democratic presidential candidates, told the head of the national party Thursday that he's in this campaign for the long haul.

In a letter to Democratic National Committee Chairman Terry McAuliffe (search), Sharpton said he is staying in the race to ensure the Democratic Party platform reflects minority concerns.

"I will continue to campaign vigorously until the last day of the convention to give voice to all Americans who have been too long taken for granted by inside-the-Beltway policies and politicians," wrote Sharpton, one of two blacks in the race until Carol Moseley Braun (search) withdrew last week.

McAuliffe has said he hopes the Democratic field, currently at seven, will be trimmed by early February, when several states hold primaries or caucuses.

The reverend from New York praised McAuliffe's proposal for a March 25 event with party leaders, which Sharpton characterized as a chance to raise money to retire the debts that losing candidates incurred over their campaigns. The DNC, however, had a different take on the so-called "unity" event, at which former presidents Clinton and Carter are expected to appear.

"It is a DNC fund-raiser for the DNC and the nominee," said DNC spokesman Tony Welch.

Campaign finance law prohibits national political parties from paying more than $5,000 to each of the candidates.

Sharpton has run his presidential campaign on a shoestring budget compared to the major candidates, who have raised and spent millions of dollars. Federal Election Commission reports show Sharpton had raised $258,729 through September.

Sharpton doesn't travel nearly as often as other candidates but has appeared in most of the debates, causing a stir more than once by challenging his rivals on issues of race or the Iraq war.