President-elect Obama is waging a charm offensive on congressional Republicans. In recent days he has personally called at least a dozen ranking GOP members of committees he will need to work with next year.

The highly personal, hands-on approach marks a change for Obama, who has been described as self-contained and aloof and who, on the campaign trail, often seemed more comfortable speaking to large rallies than in intimate settings.

Some of these Republicans, who are poised to represent their party on issues ranging from the economy to healthcare to homeland security, say it is the most aggressive outreach from an incoming president that they can remember.

“It appears to me that he has made a very genuine and aggressive attempt to reach out,” said Sen. Judd Gregg (N.H.), ranking Republican on the Senate Budget Committee, who received what he described as “a very nice courtesy call” from Obama.

“He said he wanted to work with me and I said that I wanted to be as constructive as possible,” said Gregg, describing the conversation. “I very much appreciate it. I think there’s not any question it makes a difference. It sets the right tone and it’s the way to get things done.”

Rep. Pete King (N.Y.), the top Republican on the House Homeland Security Committee, said that Obama’s earliest calls to Republicans with power over economic and security issues shed light on his priorities for the 111th Congress.

“It shows that he’s focusing on security and the economy,” said King. “I welcome the outreach.”

King said he was surprised by the unassuming tone of the voice mail message he received from Obama, noting that the president-elect recorded his name “slowly, as though I would confuse him with somebody else.”

The friendly gestures seem to be having positive effects. King told Obama that he would not take any political shots at the incoming president.

To be sure, Obama is enjoying a honeymoon period in the weeks following his record-breaking Election Day victory. Longtime political observers expect the partisan sniping to begin soon.

But Obama’s personal style shows he is willing to risk some bruising to his presidential ego: Rep. Ileana Ros-Lehtinen (Fla.), the ranking Republican on the House Foreign Affairs Committee, hung up on the president-elect when she wrongly suspected herself the victim of a prank call.

One Republican called it the biggest effort to engage Congress since former President Ronald Reagan.

“I think this seems to be a significant level of reaching out compared to other administrations, both Republican and Democratic,” said Rep. Dave Camp (R-Mich.), who is slated to take over the highest GOP post on the Ways and Means panel.

While Camp has yet to field a call from Obama, he has received plenty of attention from incoming White House Chief of Staff Rahm Emanuel and incoming Secretary of Health and Human Services Tom Daschle.

Daschle spoke with Camp about some of his broad goals for healthcare reform, and Camp said they agree on the need for more public-private partnership.

Not all ranking Republicans, however, have received personal calls, hinting at which ranking Republicans Obama sees as his most promising allies or most formidable opponents.

As of the beginning of this week, Obama had yet to call Rep. John McHugh (N.Y.), incoming ranking Republican on the House Armed Services panel, and Rep. Frank Lucas (Okla.), incoming ranking Republican on the House Agriculture Committee.

Rep. Jerry Lewis (Calif.), ranking Republican on House Appropriations, and Rep. John Mica (Fla.), ranking Republican on House Transportation and Infrastructure, were also awaiting calls, according to GOP aides.

On the Senate side of the Capitol, Obama has not called Sen. Kay Bailey Hutchison (Texas), incoming ranking Republican on the Commerce Committee, and Sen. Saxby Chambliss (Ga.), ranking Republican on Agriculture.

Obama has also called GOP leaders in the Senate and House. He caught Senate Republican Leader Mitch McConnell (Ky.) on his cell phone while he shopped at a Kroger grocery store in Louisville.

“I told the president-elect that I’ll be here to work with him once he takes office,” McConnell said, describing his conversation during a Senate floor speech.

“I think both of us are eager to confront the challenges ahead. And I told him he can expect cooperation on the confirmation of qualified nominees to key Cabinet posts.”

While Obama disagrees with powerful Republican lawmakers on a range of issues, he has sought to find common ground in his personal conversations.

Obama and Sen. James Inhofe (Okla.), the ranking Republican on the Environment and Public Works Committee, disagree strongly on global warming, which Inhofe has called a hoax. Obama avoided the potential stumbling block during his chat with Inhofe by focusing on their mutual desire to increase national infrastructure spending.

“One of the areas where Sen. Inhofe has worked across party lines is transportation,” said an Inhofe aide. “He and Obama spoke about the need for transportation infrastructure.”

Click here for a chart listing Republican members contacted by President-elect Obama.