The field vying for the Republican Party’s 2008 presidential nomination got even more crowded this week when 5-term Colorado congressman Tom Tancredo entered the race on Monday in an on-air radio announcement in Des Moines.

Tancredo, a former schoolteacher and Education Department appointee under Presidents Ronald Reagan and George H.W. Bush, has been the most vocal opponent on the Hill against illegal immigration since he took office in 1999. Until recently, Tancredo had chaired the 104-member bipartisan House Immigration Reform Caucus (now headed by California GOP congressman Brian Billbray).

Tancredo may be viewed in GOP circles as a single-issue candidate, but the congressman has been a consistent voice for change on this issue, which has significant support among the Party’s conservative wing. The Republican congressman has frequently levied the harshest of criticisms at his own party members, leadership, and President George W. Bush for not enforcing America’s federal immigration laws and for neglecting to secure its ports and borders.

In early surveys taken before Tancredo announced his candidacy, the Congressman was polling in the low single digits in most states. Tancredo polled at 2 percent in a January Zogby poll of likely GOP Iowa caucus voters and 1 percent in each of the last three American Research Group polls of Hawkeye State republicans. In a recent ARG poll in his home state of Colorado, Tancredo scored 7 percent of the support of likely GOP voters.