Four Democratic candidates announced Tuesday that they will not participate in the Michigan presidential primary on January 15 because the nominating contest was being held too early, Michigan election officials said. Senator Barack Obama (Illinois) and former Sen. John Edwards of North Carolina - the two top rivals to front-runner Sen. Hillary Clinton told state officials they would not take part, said Kelly Chesney, a spokeswoman for the Michigan secretary of state. New Mexico Governor Bill Richardson and Senator Joe Biden (Delaware) also informed the state they would not participate, she said. The four pledged earlier not to campaign in states that hold nominating contests early in violation of party rules. Clinton had not signed an earlier pledge to avoid the state contest. She has until this afternoon to decide whether to participate. Michigan and Florida have come into conflict with the Democratic National Committee by moving their nomination contests to earlier dates that conflict with the party's calendar. The committee has threatened to withhold delegates from those states at the party convention next summer that will nominate the Democratic candidate in the November 2008 election. Iowa, New Hampshire, South Carolina and Nevada will all hold early primaries and caucuses in cooperation with the DNC. "This is an extension of the pledge we made, based on the rules that the DNC laid out. We still hope that Michigan Democrats can adopt a process that meets DNC rules,” said Jen Psaki, a spokeswoman for Obama. Biden campaign manager Luis Navarro said in a statement, “Today's decision reaffirms our pledge to respect the primary calendar as established by the DNC and makes it clear that we will not play into the politics of money and Republican machinations that only serve to interfere with the primary calendar.”