Dick Lugar could see his 36-year Senate career come to an end Tuesday in the Indiana Republican primary as voters decide whether to send him back to Congress for another six-year term or bank on challenger Richard Mourdock.
Mourdock, the state treasurer, has positioned himself to the political right of Lugar and has been buoyed by the tea party, which shares his belief that the senator has become too moderate to represent the state.
In the election's final days, Lugar's campaign championed a new central message: that the senator is more electable than his opponent in the general election, where the primary winner will face Indiana congressman Joe Donnelly.
"Democrats understand Joe Donnelly will beat Richard Mourdock," Lugar wrote in an email message to supporters Sunday. "This is serious. Losing our Indiana Senate seat to the Democrats is not a risk that Republicans can take."
Publicly-available polls suggest Lugar is in serious danger of losing his seat, in part due to the support Mourdock has received from outside groups.
The election is one of the first major tests of the tea party's power this election cycle. FreedomWorks, the Tea Party Express and other national, state and local tea party groups have heavily invested in and mobilized support for Mourdock.
Voters in Wisconsin and North Carolina also head to the polls Tuesday.
North Carolina holds its state primary Tuesday, when voters will also decide on the proposed Amendment One to the state constitution, defining marriage between one man and one woman as "the only domestic legal union that shall be valid or recognized."
A survey from Public Policy Polling suggests the amendment has strong support in the state, but it's unclear whether a spate of competitive Democratic legislative races in the state will boost Democratic turnout and help defeat Amendment One. Some opponents argue that the amendment oversteps its aim to preserve traditional marriage because it bans civil unions and domestic partnerships instead of focusing solely on "same-sex marriage."
Vice President Joe Biden drew attention to the issue of gay marriage and the North Carolina vote Sunday by stating he is "absolutely comfortable" with same-sex marriage. That sentiment was echoed Monday by Secretary of Education Arne Duncan and top Obama adviser David Axelrod, who used the issue to contrast the president with Republican presidential frontrunner Mitt Romney.
"There couldn't be a starker contrast on this issue than with Gov. Romney, who has funded efforts to roll back marriage laws in California and other places," Axelrod said on a conference call with reporters. The former Massachusetts governor would "take us backward, not forward" on the issue, he added.
Romney has repeatedly stated support during this campaign for a federal constitutional amendment to ban gay marriage and believes the issue should be handled at the federal level.
In Wisconsin Tuesday, voters will choose candidates in the recall election of Gov. Scott Walker, who is being targeted by the left after waging war on public employee unions last year.