Once a leader of Colorado's term-limits movement, Republican Rep. Tom Tancredo (search) said Wednesday he's scrapping his pledge and will seek a fourth term. He cited what he called the ongoing threat posed by U.S. immigration policy.

Tancredo said he does not feel he's betraying voters. He noted he sent supporters a letter before the 2002 election saying he no longer felt bound by the term-limits pledge he made before his 1998 election.

"I concluded that term limits were a bad idea," he told The Associated Press. "There are certain issues you cannot do effectively. For better or worse, I am the most highly visible member of Congress on the issue of immigration."

Tancredo, a vocal supporter of stricter immigration enforcement, said he will stay in Congress as long as he feels useful.

The 6th Congressional District is considered one of the safest Republican seats in the state. His only opponent so far is a Democrat, businesswoman Joanna Conti, who founded an organization to help children in developing countries.

Paul Jacob, senior analyst for U.S. Term Limits (search), which lobbies for limits nationwide, said Tancredo broke the faith with voters: "I think he's a poster child for the need for term limits."

Tancredo has been an outspoken figure in the national debate over immigration policies. He angered President Bush in 2002 by accusing the president of advocating an "open door" border policy and amnesty for illegal immigrants. The president accused Tancredo of being disloyal.