As the Tea Party continues to challenge comfortable incumbents across the country, Gov. Sarah Palin has shaken up the race for U.S. Senate in Indiana by endorsing state Treasurer Richard Mourdock over Sen. Richard Lugar in the Republican primary.

Palin wrote on her Facebook page:

Richard Mourdock is the conservative choice for Indiana. Senator Lugar’s 36 years of service as a Senator are appreciated, but it’s time for the torch to pass to conservative leadership in Washington that promises to rein in government spending now.

One of the biggest issues in the campaign--aside from a controversy about Lugar's residency--has been Lugar's support for both of President Barack Obama's Supreme Court nominees, despite concerns about their left-wing records and philosophical beliefs.

Palin's emphasis on conservative beliefs reflects the debate that is taking place within the Republican Party in Indiana and nationwide, as well as a general weariness--shared by all voters--with long-term incumbents.

The endorsement carries great weight with the Republican grassroots, and could play a decisive role in the May 8 contest.