According to denverpost.com: “Sources close to the Tancredo campaign confirmed this afternoon that the Littleton Republican intends to officially announce his exit from the race at a Thursday press conference in Des Moines, Iowa.”
I think that Tancredo simply ran to make immigration a campaign issue rather than to win the nomination, and he succeeded. However, it remains to be seem how the remaining candidates who concentrate on immigration will fare when it comes to the general election. My guess is that they would be best to not try to “out-Tancredo Tancredo.”
On a related note, Tancredo also recently announced that he will not be running to keep his seat in the House.