(CNN) - With one week to go until Utah's primary, one of the two Republican Senate candidates in the race is getting a major endorsement.
The national Tea Party organization Tea Party Express Tuesday backed Mike Lee in the battle to succeed fellow Republican Bob Bennett.
The move comes four days after Bennett endorsed Tim Bridgewater, the other candidate in the contest.
Bridgewater and Lee finished first and second last month at the Utah Republican party convention, advancing to the June 22 primary. Bridgewater and Lee touted themselves as more reliable conservatives than Bennett, who finished third in the voting by delegates, eliminating him from advancing to the primary and ending his chances of re-election for a fourth term in the Senate. Bennett became the first sitting senator to go down to defeat in a primary season marked by a strong anti-incumbent sentiment.
"Mike Lee is a proud constitutional conservative who can be trusted to uphold the principles of the tea party movement," says Amy Kremer, Director of Grassroots & Coalitions for the Tea Party Express, in a statement.
Tea Party Express, best known for its three national bus tours, pumped more than half a million dollars into the recent fight for the Nevada Republican Senate nomination, helping transform former state lawmaker Sharron Angle, once a long-shot, into an easy winner in last week's primary election.
FreedomWorks has also endorsed Lee, and its volunteers are assisting in get out the vote efforts on the ground in Utah. FreedomWorks is a nonprofit conservative organization that helps train volunteer activists and has provided much of the organizational heft behind the Tea Party movement.
In endorsing Bridgewater Friday, Bennett said that "I am impressed by the fact that he, like me, brings a businessman approach to political issues."
Bennett upset many conservatives with his vote in 2007 in favor of President George W. Bush's plan for a pathway to citizenship for some illegal immigrants, and his 2008 vote in favor of the federal bailout of large banks and financial institutions.
The fiscally conservative Club for Growth actively worked to defeat Bennett, as did local Tea Party organizations and Tea Party Express. The group's third cross country bus tour included stops in Utah in March, where Tea Party Express leaders urged Republican voters to defeat Bennett in his bid for re-election.
The GOP dominates statewide elections in Utah and the winner of the Republican primary will be considered the favorite to win the general election in November.
–Follow Paul Steinhauser on Twitter: @psteinhausercnn