WASHINGTON (CNN) -- Kansas Sen. Sam Brownback formally announced Saturday he will seek the Republican presidential nomination in 2008.

Brownback, who is an outspoken opponent of abortion rights and same sex marriage, is expected to try and define himself as the true conservative Republican in the GOP field. He often describes himself as an admirer of the late President Ronald Reagan.

In addition to pledging never to sign a tax increase as well as vowing to restore fiscal discipline to the federal budget process, Brownback also invoked God in his announcement speech in Topeka, Kansas.

"The last thing we need in America is to take God out of our public lives and institutions," Brownback said. "We need to embrace our nation's motto 'In God We Trust,' not be ashamed of it. Search the record of history. To walk away from the almighty is to embrace decline for a nation. To embrace him leads to renewal, for individuals and for nations."

Brownback recently won re-election to the Senate in 2004. He was first elected to the House in 1994 and was elected to the Senate in 1996 to fill the final two years of Senate Majority Leader Robert Dole's, R-Kansas, unexpired term. Dole retired from the Senate that year to focus on his presidential campaign against President Bill Clinton. Brownback won his first six-year Senate term in 1998.