Embattled Indiana Republican Sen. Dick Lugar has fallen behind his Tea Party challenger in a new poll that finds the veteran legislator in danger of losing after 36 years in office.

The Howey/DePauw Indiana Battleground Poll released Friday puts Lugar a stunning 10 points behind state Treasurer Richard Mourdock, trailing 38 percent to 48 percent. It surveyed 700 likely voters from April 30 to May 1 and has a margin of error of plus or minus 3.7 percentage points.

Voters go to the polls Tuesday.

Lugar has been one of Indiana's most popular political figures for decades, and had a reputation as a statesman of running clean, positive campaigns. But with Mourdock riding the Tea Party's enthusiasm and putting Lugar's political life in jeopardy for perhaps the first time, Lugar fired off a string of negative attacks.

They don't appear to have worked, and on Friday Lugar was trying a more positive approach in a new TV ad aimed at getting out the vote and stemming Mourdock's surge.

"America faces serious challenges, but Hoosiers' courage and determination are unbreakable," Lugar says in the spot. "It's this spirit that guides me every day in the Senate."

He goes on to list the conservative agenda points that Mourdock has said he has failed on, arguing that he's worked hard to "overturn Obamacare," to protect "our energy security" and to "destroy and keep from terrorists thousands of rogue nuclear and biological weapons."

Tuesday will tell if the reminder of what Hoosiers liked about Lugar for so many years will be enough.