Dick Lugar, the Senate's longest-tenured Republican, is in the midst of his toughest campaign of the past 30 years.

With the help of outside groups aligned with the Tea Party movement, state Treasurer Richard Mourdock stands a good chance of unseating Lugar in Tuesday's primary and becoming the Senate's newest fiscal hawk in January.

Along with Utah, it's one of two notable conservative-vs.-establishment Senate primaries this year, after 2010 saw upsets in Alaska, Delaware, Nevada and Utah as Tea Partiers across the country gave incumbents a scare. This year, conservatives have targeted Republicans Lugar and Orrin Hatch, who ties Lugar atop the Senate GOP's seniority list. Hatch of Utah is surviving, so far; Lugar, meanwhile, faces the strongest primary challenge to a Senate incumbent in 2012.

In Mourdock, Lugar faces a mild-mannered statewide officeholder who wants to eliminate federal agencies and cut more spending than Rep. Paul Ryan, R-Wis., would.

After the Tea Party wave has seemed to fade post 2010, what is this election telling us?

WHAT THE RACE MEANS

• Same Story, New Year. Conservatives can still pick their spots and threaten incumbents, following the same script they used in 2010. In Indiana, FreedomWorks and the Club for Growth have replayed their standard playbook, choosing a state that's not terribly expensive and attacking an incumbent for moderate votes. In Indiana, that means Lugar's votes for TARP, against an earmarks moratorium, and in favor of Supreme Court justices Sonia Sotomayor and Elena Kagan. Lugar has spent $6.7 million to Mourdock's $2 million defending himself, with Mourdock's PAC and super PAC backers ($2.9 million) outspending Lugar's ($1.7 million).
• Pouncing on a Weak Incumbent. Lugar has his own problems, regardless of anything Mourdock has said or done. Lugar was briefly ruled ineligible to vote in the county where he was registered, after selling his home in the late 1970s and moving to Washington, D.C. He repaid the Treasury after using taxpayer money for hotel stays during trips back to Indiana. It resonates differently in Indiana in 2012 when Mourdock and the Club for Growth claim Lugar cast those votes because he's "out of touch" with Indiana. Candidates who lost to Tea Partiers in 2010 didn't have such pronounced liabilities.
• Which Super PAC Is That, Again? The panoply of election spenders - 12 groups have spent $4.6 million on this race - foretells more attack groups forming around non-presidential campaigns, and perhaps disappearing quickly.  The pro-Lugar Hoosiers for Jobs and the Economy and the Indiana Values SuperPAC each formed earlier this year, in Sacramento, Calif.,  and D.C. respectively, and have run ads attacking Mourdock. The USA Super PAC, which supports Mourdock and is the only group spending in Indiana that was formed in the state, was launched in April by Citizens United lawyer James Bopp. These groups have been significant players along with Mourdock backers FreedomWorks, the Club for Growth, the National Rifle Association and the pro-Lugar American Action Network.
• The GOP Is Still Getting More Conservative. Mourdock is as fiscally conservative as they come, and even with Lugar's weaknesses, it will say something if Republican voters pick him. "The election isn't really about Richard Mourdock; it's more reflective of the internal changes in the Republican Party," former Democratic Indiana Sen. Evan Bayh suggested last week. Lugar supports Paul Ryan's budgets and entitlement changes, which only recently would have given him notable conservative bona fides, yet his opponents have put him at risk by calling him too moderate.