On Tuesday, primaries in Kentucky, Arkansas and Pennsylvania will test a number of theories propagated by pundits and political strategists in recent months. Will Tea Party enthusiasm translate into votes? Will the Democrats and Republicans become more ideologically pure, or will voters tilt both parties to the right? What does this all portend for the midterm elections? Here's what to watch for on Tuesday:

  • The State-By-State Breakdown  John Harwood at The New York Times explains the basic dynamics at play:
In Kentucky, Rand Paul’s bid for the Republican nomination will again test the strength of the Tea Party right against the establishment, represented by Trey Grayson.

In Arkansas, Lt. Gov. Bill Halter’s attempt to oust the incumbent Democrat, Senator Blanche Lincoln, will measure the left’s resistance to compromise in the age of Obama.

In Pennsylvania, the fight by Senator Arlen Specter, the Republican turned Democrat, to hold off Representative Joe Sestak for his new party’s nomination will show whether the combination of incumbency, age and partisan inconstancy is simply too much to bear.
  • All Eyes on the Tea Party, writes Jeff Zeleny in The New York Times: "Both parties will study the results for evidence of the Tea Party movement’s ability to translate passion into votes. They will gauge the degree to which President Obama, who is backing Mr. Specter and Mrs. Lincoln, is a political liability or benefit to his party. And they will look to see what messages, if any, assuage voter anger and anxiety as politics hurtles toward the fall, the economy still in the shadow of the recession."
  • We'll Be Able to Define Anti-Government Rage, write Dan Balz and Chris Cillizza in the Washington Post: "Everyone has a different definition of the anger: anti-incumbent; anti-Obama; anti-establishment; anti-Washington. But the expressions of displeasure are everywhere. Some voters think Washington is spending too much and is infringing on their rights. Others say Washington is not doing enough -- to penalize bankers or to oversee the cleanup of the Gulf of Mexico as oil gushes from a broken well."
  • GOP Populism Coming in Vogue, writes Jonathan Weisman at The Wall Street Journal: "GOP leaders in Washington, responding to an angry and demanding Republican electorate, are adopting more populist economic policies, lambasting a wider swath of Obama administration policies as 'government takeovers' and vowing dramatic fiscal changes."
  • Ideological Purity? Don't Bet On It, writes E.J. Dionne in The Washington Post: "With incumbent Democratic senators under threat in two more primaries on Tuesday, the conventional view is that Republicans and Democrats will emerge from this election more ideologically polarized than ever. Primaries will push Republicans to the right and Democrats to the left. That's only half true. Republicans will, indeed, end the year a more philosophically coherent right-wing party. But the Democrats will, if anything, become more ideologically diverse." He points to a number of Democratic races where the likely outcomes vary across the ideological spectrum. In Pennsylvania's special election, for instance, the late Rep. John Murtha looks to be succeeded by  a more conservative candidate.