Sen. James Inhofe has worn a lot of hats in his decades-long political career — firebrand conservative, global-warming skeptic and defender of earmarks, to name just a few.

But the Oklahoma Republican might be facing his most challenging role yet as he works to bridge the sizable gap between Senate and House Republicans over reauthorizing federal transportation programs.

Senate Environment and Public Works Chairman Barbara Boxer (D-Calif.), who is on her second go-round with Inhofe on writing a transportation bill, praised the role the committee’s ranking member has played.

“It’s bridging the gap between House Republicans and the bipartisan Senate approach. There’s no divide between Sen. Inhofe and I, and it’s been a very important effort I think,” Boxer said.

Inhofe “has been just the best partner for me as chairman … in the best traditions of how the highway bill has been done until now,” she added.

Inhofe argues that there are only two major differences between this conference committee and the one he chaired in 2005, the last time a transportation bill was passed.

“Republicans were [in the] majority, and I was chairman. So we pretty much ran this thing in a way that was in concert with the House. And it’s not all that different now,” Inhofe said.

The key differences, according to Inhofe, have been “the lack of a House bill” and the fact that “we’ve got a lot of new people, and they’re not familiar with the process. … Back in ’05, they’d all been through it and they knew what the process was.”

That has forced him into a new role, acting as a diplomat to the House, where he served from 1987 to 1994.

Over the past several weeks, Inhofe has engaged the House conferees to find common ground and bring them along to the notion that the Senate’s bill has much of the conservative agenda’s items in it.

For Inhofe, part of the problem is that so many of the Republicans on the conference committee have committed themselves to an incredibly narrow view on spending.

“They would like to be against anything with a lot of zeros in it,” Inhofe said, arguing that this mindset is ultimately counter to the conservative position.

“There is a conservative position in this. And that is to have a bill. Because if you don’t have a bill, there’s only one other choice, you have to do extensions.” And those, he said, result in “throwing away a third of the money that should be spent on highways. And I just can’t let that happen.”

In his conversations with freshmen and other House conferees, Inhofe has said, “And this comes from my heart. I told these freshmen that I’m still in shock that Barbara Boxer worked so close with me on these reforms,” things like transportation enhancements and other changes to highway and transit programs that have long been sought by Republicans.

“I told the young people, ‘We’re starting way ahead than I thought we’d have to start,’” Inhofe said.

House Transportation and Infrastructure Chairman John Mica (R-Fla.) praised Inhofe’s efforts.

“We have a great working relationship,” Mica said, adding that Inhofe is “very actively engaged and trying to bridge the gap between the House and the Senate.”

In fact, most House conferees agreed  that Inhofe has done a good job of reaching out to them — something many have complained has been lacking from most Senators. “Sen. Inhofe has done a good job,” Rep. Bill Shuster (R-Pa.) said.

Rep. James Lankford (R-Okla.) called Inhofe a “rock-solid conservative [who is] using his credentials to come over to the House. … I think people listen to him.

“He’s worked hard to make a bipartisan agreement over there, and now it’s time to get a bicameral one,” Lankford added.

But for House Republicans, that difference between a Senate bipartisan deal and a bicameral agreement is the chief sticking point.

“This is a bicameral process, and while I understand it was bipartisan over there, I’d like both he and Sen. Boxer to engage more with the House and get a real give-and-take going,” Shuster said.

Lankford agreed, warning bluntly that “the guys I’m talking to over here say, ‘It’s great to hear from the Senator, but I’m not accountable to him. I’m accountable to my constituents.’”

Rep. Steve Southerland (R-Fla.), who, like Lankford, is one of a handful of freshmen on the conference, complained that Members from the “upper chamber” have not appeared interested in engaging with the House counterparts. “I’ve noticed that a common theme among Senators, as well as the president, [is] to ignore that there’s a people’s House,” Southerland said. He noted, “I’ve been to five working group meetings, and I still haven’t seen a Senator. I wouldn’t give my voting card to another Member, and I’m not going to hand that responsibility over to my staff.”

Inhofe adamantly disagreed with the notion that the Senate is not interested in a bicameral bill.

“No, no, we’re not doing that. We’re soliciting from them … what they want to do,” Inhofe said, chalking up part of the frustration to the fact that “we [went] into conference with a bill on our side and a skeleton on their side,” meaning that the Senate was much further along in passing a full reauthorization measure than the House.

“While we had a bipartisan bill over here, we didn’t have a bicameral one. And we’re getting that now,” Inhofe stressed.

Despite all of this, there are signs of life.

On Tuesday, Boxer and Inhofe released a partial compromise proposal that, while not touching issues such as the Keystone XL oil pipeline, does include a number of reforms sought by the GOP. House Republicans said Wednesday they plan to send a counter offer before the end of the week.

And that movement, no matter how small, is encouraging. “Before, it’s been a lot of talk, a lot of theory. But now it’s time to get moving,” Lankford said, adding that House Republicans are committed to not “stalling this out.”

Boxer also said she remains optimistic a bill can be completed quickly, arguing her relationship with Inhofe is one of the reasons for hope.

“The two of us coming from these very different places have teamed up. So there’s no reason on God’s green earth why it should be problematic,” Boxer said.