Washington -- The poll numbers say he's struggling, and well-known conservatives are racing to endorse his opponent. Sen. Dick Lugar, of Indiana, faces Republican primary voters Tuesday, and he's in serious trouble.
Sen. Orrin Hatch, R-Utah, is working to avoid a similar fate in coming weeks.
Lugar and Hatch share the distinction of being the most senior Senate Republicans, winning their first elections in 1976, and now, 36 years later, they share something else: the ire of the tea party.
The same conservative activists who helped defeat Sen. Bob Bennett, R-Utah, in 2010 have made Lugar and Hatch their top targets this year, and their arguments against the senators have been almost identical.
Opponents have painted Hatch, 78, and Lugar, 80, as out of touch and more willing to negotiate with Democrats than to hold the line on spending. "Retire Hatch" and "Retire Lugar" yard signs hint at their age, and their opponents - former state Sen. Dan Liljenquist in Utah and state Treasurer Richard Mourdock in Indiana - share a slogan: "It's time."
But beyond these similarities are some vast differences that point to why Lugar may see his career end late Tuesday and why Hatch is seen as the favorite to win his party's nomination in late June.
Political observers say Hatch and his supporters were quicker to attack his challengers and to curry favor with conservatives. He also faced attacks from fewer outside groups and, frankly, made fewer blunders than Lugar.
"I don't think they anticipated the strength of the opposition they have encountered," said Leslie Lenkowsky, an Indiana University professor who specializes in state politics and considers himself a Lugar supporter. "Some people on the Lugar campaign staff might have been a little too arrogant."
Mourdock didn't look that threatening in the beginning. He was a perennial candidate who had lost four elections before winning two terms as state treasurer. His claim to fame was suing the federal government over the bailout of the auto industry, a move that would also prove to be a liability in a state with strong ties to carmakers.
But tea party groups like FreedomWorks and the Club for Growth embraced him, and Lugar had little success in changing the mind of disaffected Indiana Republicans, particularly while Mourdock and his allies hammered him for spending too little time in Indiana.
Then the residency scandal hit, or what Lenkowsky refers to as the "unforced error" that rocked the race.
A county elections board, controlled by Democrats, ruled in March that Lugar could not vote in his home precinct because he registered using the address for an Indianapolis home he sold in 1977. He had no actual residence in the state and later reached a deal that allowed him to change his voting registration to a family farm elsewhere in Indiana.
From there, Mourdock started attracting major endorsements from Sarah Palin to Michele Bachmann to Grover Norquist and Americans for Tax Reform.
The most recent survey, conducted by Howey Politics Indiana and DePauw University, showed Lugar 10 percentage points behind.
Robert Vane, a spokesman for a super political action committee supporting Lugar, credits the residency scandal with giving Mourdock the lead. As does FreedomWorks' Russ Walker, who said "it had a huge impact."
But they agree on little else.
Vane argues the race remains "an utter toss-up," in part because of a last-minute call for an investigation into Mourdock's actions as treasurer. Walker says Lugar is done.
"Voters are going to decide it is time for new leadership," he said.
Walker is FreedomWorks' point man in Utah, though he has campaigned extensively in Indiana as well. He argues that Lugar has been far less aggressive than Hatch and Hatch's surrogates have been more willing to take shots at Liljenquist.
"Lugar reacted much more like Bob Bennett did," Walker said.
Bennett was slower to take the tea party seriously and made no attempt to attack his GOP challengers. He came in third at the 2010 state Republican convention. Sen. Mike Lee eventually won the race.
Utah's multistep election process, which starts with the election of delegates, then goes to a state convention and possibly a primary before November's general election, has allowed Hatch to show his strength. Indiana's slow push to a primary has worn down Lugar.
But now that it is just Hatch versus Liljenquist, Walker hopes Utah will follow the Indiana script.
"I think it is a new game here," he said. "I am very optimistic that Utahns are going to come to the same realization Hoosiers are coming to this week."
Hatch's campaign manager, Dave Hansen, says "it is apples and oranges to a great degree," but he has been keeping an eye on Lugar.
"It seems like the Indiana race has been Senator Lugar starting on top and a gradual drop since then," Hansen said. "In the Hatch race, our starting point was probably our lowest point and it has continued to go up from there."
He also noted that Lugar had to fight off the opposition of a number of conservative groups, while Hatch's opposition is more limited.
"It is just one renegade group out here," Hansen said, referring to FreedomWorks.
While Hatch has the support of the National Rifle Association, Lugar does not. Hatch has also benefited from the endorsement of conservative talk radio personalities and more importantly Mitt Romney, the presumptive Republican presidential candidate and a political superstar in Utah. Lugar doesn't have that backing.
Outside groups have spent $4.8 million on Indiana's Senate race. Opponents to Lugar only have increased their spending in recent days, while the American Action Network, a group backing the senator, has backed away. So far, outside groups have spent closer to $1.5 million in Utah, and more than half of it has supported Hatch.
More telling than anything is that Lugar has started encouraging independents and Democrats to vote in his state's open primary, a sign he's not confident he can win if only Republicans go to the polls.