INDIANAPOLIS — By now, state Treasurer Richard Mourdock should know when to hold his tongue.

But the Republican Senate nominee, who’s been in Indiana politics for more than two decades, has a habit of speaking freely, frequently.

Many Hoosiers agree with his ideology, but Mourdock’s errors are political. As a result, less than two weeks before Election Day, Mourdock’s greatest hurdle to winning a Senate seat is himself.

“Richard doesn’t really believe in a filter,” said one Hoosier Republican and Mourdock ally, who declined to criticize the nominee on the record. “He is who he is and refuses to compromise for expediency.”

On Tuesday evening, Mourdock described pregnancy that results from rape as “something that God intended to happen” in response to an open-ended question on abortion. He delivered a tearful apology the next day to those who misunderstood his comments, which he described as not “articulate.”

The comments sent the Indiana race into turmoil two weeks before Election Day, just as Mourdock regained his footing against Rep. Joe Donnelly (D) following a rocky September for Republicans nationwide. But even before this week’s Senate debate, Hoosier operatives from both parties still anticipated a single-point race.

“It is a closer race than what we anticipated,” Sen. Dan Coats (R-Ind.), who’s known Mourdock for 25 years, said on Tuesday afternoon. “I think he’s had an uphill battle to try to define himself as who he really is.”

In traditionally GOP parts of the state, such as the southern tier, Mourdock’s intentions attract sympathy and support. Almost half of the state’s voters view themselves as conservatives, recent polling showed. Driving from the debate site in New Albany, in the state’s southern tip, to central Indianapolis, the interstate is lined with anti-abortion billboards.

Mourdock’s greater challenge in winning votes Nov. 6 lies in the collar counties around the capital city of Indiana, known as the “Crossroads of America.” More moderate Republicans occupy the posh suburbs and small towns — and many of them still revere the man Mourdock defeated in the GOP primary, Sen. Dick Lugar.

Many of Mourdock’s woes began after his bruising and expensive primary to defeat Lugar. The Senator’s operation never was able to capitalize on Mourdock’s loquaciousness and use it as political ammunition. During the primary, often only video trackers from Democratic groups were watching Mourdock.

On his post-primary victory tour, Mourdock let this line slip in an interview with NBC: “To me, the highlight of politics is to inflict my opinion on someone else.”

Democrats clipped the video and put it in a TV advertisement that aired throughout the state for months. Those 14 words,  along with a couple of more televised glibs, gave the party a head start in defining Mourdock in the general election.

It worked. Throughout the state, voters echo the sentiment in that spot.

“I don’t like Mourdock too well,” said Steve Ferguson, a 65-year-old registered Republican sipping coffee on the sidewalk in Madison, Ind. “We need someone who can compromise once in a while. So I’ll vote for the other guy.”

“I just don’t care for Mourdock’s beliefs,” said truck driver Jeremy Kelly, 32, an independent from the Indianapolis metro area. “Donnelly is not my favorite either. But it’s the lesser of the evils.”

Mourdock accused Democrats of taking his interview comments out of context. But Mourdock’s error shows he’s always had trouble speaking carefully — a learned political skill for most 20-year veterans of elected office.

Unfortunately for Republicans, they have seen this problem before. In 2010, several second-tier GOP nominees made gaffe after gaffe, costing the party control of the Senate with their eventual losses in Nevada and Colorado.

But Mourdock has more high-caliber political experience than those candidates. Democrats attempted to paint Mourdock as a tea party star, but the Republican has been around local politics since his first bid for Congress in 1988.

Coats described Mourdock as someone who “literally came out of the establishment.”

“His whole political career has been working with the Republican establishment,” Coats said. “As a Member of [Gov.] Mitch Daniels’ team on the state level, he was very popular. In fact, he was top vote-getter.”

Since the primary, at least 10 of Coats’ colleagues marched through Indiana to campaign for Mourdock. An 11th, Sen. Kelly Ayotte (R-N.H.), canceled her Wednesday visit after Mourdock’s comments.

Lugar has visited the state twice in recent weeks, including a trip to stump for the GOP’s state attorney general. But his spokesman confirmed he has no plans to campaign for Mourdock.

Local Republicans are taking note. Bud Pfeiffer, a jewelry store owner in Salem, said he thought Lugar would have campaigned for Mourdock by now.

“He still has a lot of weight,” said Pfeiffer, a Mourdock backer. “He has a lot of power still.”

Donnelly takes every opportunity to name-drop Lugar on the campaign trail, including mentioning the senior Senator’s name almost 10 times during a Saturday afternoon interview at McGinley’s Golden Ace Inn. The almost windowless, family-owned bar on Indianapolis’ east side hosts Notre Dame fans, including Donnelly, on weekends for a “Coney Bar.”

“I’ve never been on a ballot against Richard Lugar,” said Donnelly, drinking a Diet Coke and periodically checking the score when the crowd roars. “And by my presence on that ballot, we were able to make sure that someone in Dick Lugar’s tradition would be able to serve in the U.S. Senate.”

The GOP has another fear on the ballot: libertarian Andrew Horning. Historically, the libertarian Senate candidate garners 1 percent to 6 percent in a three-way race — votes theoretically siphoned from the GOP nominee. Campaign signs for Gary Johnson, the libertarian presidential candidate, line town squares across the southern half of the state.

“I was pissed off at the way the campaign was handled — way too much mudslinging,” said Nick Hofmeister, a 50-year-old independent who describes himself as “very conservative.” He’s voting for Horning.

All of this matters if the election comes down to a single percentage point or two, which many Hoosiers predict.

“I think Joe’s ahead by 2 or 3 points,” former Sen. Evan Bayh (D-Ind.) said. “He’s in a very competitive position. But two weeks is an eternity in politics.”

More coverage of the Rust Belt Road Trip here.