As first lady and then junior senator from New York, Hillary Rodham Clinton (D) has long been at war with the Republican National Committee (RNC). But the two adversaries have recently found some common ground: attacking Sen. Barack Obama (D-Ill.).

Clinton has launched assaults on Obama made by the RNC over the past year, while the Republican Party has used lines of attack developed by Clinton to soften Obama for a possible general election contest match-up against Sen. John McCain (R-Ariz.).

For example, at the end of January, Obama’s campaign manager accused Clinton of being willing “to do or say anything to win an election,” repeating a similar statement RNC Chairman Mike Duncan made a week earlier.

But Clinton has taken the more negative approach, and at times has found an ally in the RNC’s opposition research department, much to the satisfaction of Republican officials who have battled her for years.

“There appears to be bipartisan agreement that Barack Obama is not prepared to be commander in chief,” said Danny Diaz, the RNC’s communications director.

Democrats, however, are alarmed by the trend.

“Let me say how ill-at-ease I and many others are becoming over the ear-piercing tone the campaigns may be taking,” Rep. Emanuel Cleaver (D-Mo.), a Clinton supporter, wrote in a recent letter to Democratic National Committee (DNC) Chairman Howard Dean.

In November, as she started to lose ground to Obama in Iowa, Clinton seemed to rip a page out of GOP research by ridiculing Obama’s claim that time he spent as a child abroad gave him a unique foreign policy perspective. The jab was so similar to an RNC memo that it prompted NBC News reporter Andrea Mitchell to comment that Clinton had “mimick[ed] the latest Republican attack line.”

More recently, Clinton accused Obama at a debate of being a do-nothing chairman of the Senate’s Foreign Relations European Affairs subcommittee. That attack had surfaced a month earlier in an RNC research memo noting that Obama had “held zero hearings as chairman of the Subcommittee on European Affairs.”

Clinton and the RNC have also jointly criticized Obama for waiting 11 months into his Senate career to deliver a major speech on Iraq. Republicans first hit Obama on his lack of urgency in March of last year.

Last May, Republicans were quick to blast Obama for the number of times he voted “present” to avoid casting controversial votes in the Illinois state Senate. The Clinton campaign began pressing that line frequently this year.

Chris Lehane, a former Clinton White House aide, said that Obama has also used GOP attacks to his advantage, noting that Obama’s campaign has tried at times to portray Clinton as nakedly ambitious, a tactic Republicans have employed for years.

“I would posit [a] number of criticisms Obama has made of Clinton us[ing] talking points Republicans were using for years,” he said. “I think it’s all fair.”

The Clinton campaign can point to several instances when the Obama campaign has waged what it calls “GOP-style” attacks.

On ABC’s “This Week,” senior Obama strategist David Axelrod tacitly raised Clinton’s Whitewater dealings to rebut questions about Obama’s financial relationship with indicted donor Tony Rezko.

Axelrod and Obama campaign manager David Plouffe have attempted to portray Clinton as secretive and possibly unethical for not releasing her income tax returns.  

Last week, Axelrod also demanded that Clinton make public an array of records from the Clinton Presidential Library. It was the RNC, however, that first raised the issue in November when it declared the “American people deserve to know what information is guarded in these libraries.”

But while Obama may have also borrowed GOP attack lines, Clinton has done most of the mudslinging, according to voters.

Exit polls from the Texas primary showed that 52 percent of voters believed that Clinton had attacked Obama unfairly. Only 35 percent thought Obama had done the same to Clinton.

Clinton’s core criticism of Obama in recent weeks has focused on his ability to serve as commander in chief during a time of crisis. She unveiled television ads before the March 4 primary that specifically questioned Obama’s readiness to answer a national security call at 3 o’clock in the morning, borrowing what Republicans have said will be their chief critique of Obama if he wins the nomination.

“The messages driven on Obama’s inexperience and out-of-the-mainstream record have been picked up and used because they are effective,” said a GOP official.

Darrell West, a professor of political science at Brown University, said that critiques now employed by Clinton and Obama could come back to haunt the party in November.  “It’s a risky tactic because if Obama becomes the nominee, her words could end up appearing in a general election ad,” said West, who speculated that such an ad may ask viewers: “If Democrats feel this way about the nominee, how should you feel?”

John Gilliom, chairman of the department of political science at Ohio University, said Clinton’s attacks worked well in Ohio. He said that should give Democrats concern because it portends more negative attacks from both sides. “The tone of the Clinton campaign is going to be doing some damage to the person who stands a very good chance of becoming the nominee,” he said. “That’s one of the scariest things for Democrats coming out of Ohio.”

Even Clinton supporters have voiced concern.

“The road to Denver, as it currently exists, is dotted with intra-party explosive devices (IEDs) with the potential to blow away our party’s very real chance to capture the White House,” wrote Cleaver in his letter to Dean.

Rep. Dennis Cardoza (D-Calif.), another Clinton supporter, told The Hill: “If I see either one of them [Obama or Clinton] I plan to tell them to cool the rhetoric.”

But Lehane, who is now a political consultant based in California, said those concerns are overblown.

“The primary is like thumb-wrestling compared to the steel-cage death match that the general election will be,” said Lehane, who served as spokesman for former Vice President Al Gore’s 2000 White House campaign. “The more the primary tests the mettle of a candidate, the better it will be for a general election. The nominee at the end of the process … will be battle-tested.”

Lehane said Gore was made a better candidate from having to respond to punches from his primary opponent, former Sen. Bill Bradley (D-N.J.).