Three key senatorial primaries occurring today will help gauge the country's political mood and the prospects for both parties heading into November's elections. The primaries in focus are in Arkansas, where incumbent Democrat Blanche Lincoln is challenged by Lt. Governor Bill Halter; Kentucky, where Tea Party candidate Rand Paul faces off against Secretary of State Trey Grayson to replace retiring GOP Senator Jim Bunning; and Pennsylvania, where Republican-turned-Democrat Arlen Specter is challenged by Rep. Joe Sestak. Here's what the elections mean and what to look for.

  • How Bad Is It For Incumbents? The New York Times' Jeff Zeleny writes, "Two Democratic senators, with combined Washington experience of nearly 50 years, will discover if they have assembled strong-enough coalitions to withstand an anti-incumbent surge or if their careers will effectively end. And an open Senate seat in Kentucky will help show whether Tea Party advocates can produce an electoral victory."
  • Is Fox News More Powerful Than GOP Establishment? The Washington Post's Dan Balz looks to Kentucky. "On Monday, Grayson showed the frustration of a candidate who might have thought he would have a relatively easy path to victory, with the endorsements of Senate Minority Leader Mitch McConnell (Ky.) and much of his state's GOP leaders. He said that Fox News Channel continually promoted his opponent and indirectly suggested that the network had more power within the party than the establishment itself."
  • Can the Tea Party and GOP Establishment 'Co-Exist'? The Washington Post's Chris Cillizza wonders, "If, as expected, ophthalmologist Rand Paul wins tonight in the Kentucky Republican Senate primary over Secretary of State Trey Grayson, the test will be whether the Kentucky GOP's two warring wings can come together. ... The tea party movement has, to date, resisted any attempt by the party establishment to co-opt its power -- much less take over the campaign of one of its own. Having won largely by running against Washington (and Republicans in Washington), how does Paul reconcile his past statements against the establishment with a party that knows it must rally around him?"
  • How Will Elections Predict Changing Congress? Reuters' John Whitesides writes, "The three primary election battles highlight the biggest day of voting so far in a year when opinion polls find a sour voter mood fueled by distrust of Washington and worries that neither party is doing enough to rescue the economy and restrain government spending. That mood, which pollsters say is the strongest in decades, threatens to sweep away many well-known incumbents and put Democratic control of Congress at risk in November's election when all 435 House of Representatives seats, 36 of 100 Senate seats and 37 of 50 state governorships are at stake."
  • Can Obama Still Influence Races? Politico's Jon Martin and Glenn Thrush write, "Once thought to be an unalloyed asset for most any Democratic candidate, Obama's personal involvement is no longer guaranteed - or guaranteed to succeed. In close to a dozen contests, Obama's intervention hasn't paid dividends. ... Tuesday's crop of primaries and special elections vividly illustrate the challenge for Obama: the number of races where he can have a positive impact has been narrowed by 18 months of constant political warfare, Democratic electoral defeats and his own missteps."