Lugar, one of the Senate's longest serving members, faces a tough re-election bid after some in his party questioned his conservative chops based on his decades of work in the Senate and a reputation for reaching across the aisle, The New York Times reported Tuesday.
The poll, conducted last month, indicated Lugar led state Treasurer Mourdock, 42 percent to 35 percent among likely primary voters, but the advantage was in the poll's margin of error of 5 percentage points.
Lugar, 80, told the Times his re-election situation is a product of forces beyond Indiana.
"You can say, 'Why in the world are we having such a time?'" he said. "Because there are others in America who are very interested in this, sort of as a battleground, or I'd even say a playground, for their thoughts."
Others said Lugar is in the middle of a perfect storm of opposition, the Times said. Tea Party groups and organizations such as the Club for Growth and the National Rifle Association questioning his conservative credentials. Some Indiana residents say they wonder whether Lugar has lost touch with Hoosiers. Still others mention Lugar's age.
The winner of the state's Republican primary May 8 will face U.S. Rep. Joe Donnelly in November.