Sen. Richard Lugar of Indiana has served 35 years in the Senate, casting nearly 12,000 votes.
He has been nominated for a Nobel Prize and has been considered for secretary of state. The Republican hasn't broken a sweat on Election Day since 1976, when gas averaged 55 cents a gallon and Gerald Ford was president.
Yet there was Lugar back in Indiana during the Senate's February recess, shaking hands on assembly lines, speaking at Lincoln Day dinners, conducting meet-and-greets straight out of Hillary Clinton's Listening Tour playbook. By his own count, Lugar traveled "thousands of miles" up and down the state in nine days.
"I have never been involved in a campaign that was so extensive in terms of trying to get in touch with every household in the State of Indiana," he said.
A month shy of his 80th birthday, Lugar is facing the most vigorous re-election fight of his career.
Tea Party groups in Indiana have made him their No. 1 target, saying the silver-hailed senator has strayed from Republican principles too many times.
They are backing state Treasurer Richard Mourdock, creating Lugar's first Republican primary challenge since he took office.
Another complication: Lugar's startling revelation that he sold his home in Indianapolis and bought one outside Washington shortly after winning his first election to the Senate three decades ago.
The campaign has become more than just a personal test for Lugar; it's also a referendum on his style of legislating. Lugar is a throwback to a different era in the Senate and the nation's politics. Is there still room on the national stage for a lawmaker known for compromise and bipartisanship?
"It's a style that is disappearing in the Senate," Indiana University political science professor Brian Vargus says. "And it is a style that some people, particularly in the Republican Party and in the Tea Party, on the far right, don't like."
Senate opponent Mourdock, 60, did not mince words. "Bipartisanship has taken us to the brink of bankruptcy," he said.
"We are not a time when it should be about partisanship. It is about power politics, it is about having the two sides define themselves. I think this race is going to go a long way to define the Republican Party in the U.S. Senate."
Lugar has been a dependably conservative vote across his years in the Senate, and his record has moved even further to the right as the challenge from the Tea Party became clear. His rating by the conservative Club for Growth, which has endorsed Mourdock, jumped from 54 percent in 2008, to 80 percent last year.
"I think he's tried to scramble quickly to be somebody other than who he has been for the last 35 years," U.S. Rep. Joe Donnelly, a Democrat waiting in the wings to run against the winner of the Republican primary, said.
But Tea Party supporters have not forgiven Lugar for a number of high profile votes in recent years, including his support of the 2008 bank bailout, increases in the U.S. debt limit and President Obama's nominees to the U.S. Supreme Court.
"He was the first Republican to come out for Elena Kagan and the second for Sonia Sotomayor, even before the hearings," Mourdock said. "Believe me, that will be his undoing among the primary electorate here in Indiana."
Monica Boyer, co-founder of Hoosiers for a Conservative Senate, said, "We just decided, 'This has to stop.' Those votes, they were the straw that broke the camel's back."
Hoosiers is an umbrella organization of Tea Party groups working to unseat Lugar.