Newt Gingrich and Rep. Ron Paul are engaged in a fierce battle for the GOP nomination, but it's not the first time the two veteran politicians have locked horns.

Bad blood between the two men dates back to 1995, when then-House Speaker Newt Gingrich worked unsuccessfully to deny Paul a Texas House seat in a bitter primary battle that pitted Paul against a Gingrich-backed, Democrat-turned-Republican opponent.

"He orchestrated a million-dollar campaign to keep me out of Congress," Paul told the Houston Chronicle at the time.

When Newt Gingrich took over as speaker of the House in 1994, he pursued a policy of enticing Democratic incumbents into the Republican fold to guarantee passage of GOP legislation. A deal was struck whereby Rep. Greg Laughlin switched parties in June 1995 in return for the Ways and Means seat he had been counting on before the Democrats lost power. At the same time, Paul re-entered politics to run in Texas' 14th congressional race, setting up a primary battle between he and Laughlin.

"I was pressured to support Laughlin," said Tom Pauken, who was Texas' Republican state chairman at the time.

Although Pauken held steadfast for Paul, the rest of the GOP establishment from then Gov. George W. Bush on down filed into the district with money and made personal appeals for the congressman. Laughlin reportedly said at the time that the endorsements were meant to show he had the GOP stamp of approval.

The race got nasty when an Austin marketing company, on behalf of the Republican National Committee, called people and asked respondents who favored Paul whether they would still support him knowing that he was in favor of legalizing drugs, pornography and prostitution, according to the New York Times. The paper noted that the claims weren't true.

Pauken contends that Gingrich's support of Laughlin was all about power and that Gingrich wasn't interested in building a truly conservative base. Pauken added that Gingrich's strategy backfired when voters felt a candidate was being imposed on the district by outsiders.

"People resented Gingrich, that probably played a major factor," Pauken said.

Richard Murray, a political science professor at the University of Houston, agreed with Pauken that voters were not receptive to someone switching parties, but added that Paul ran a very aggressive grassroots campaign that included phone-banking, networking and identifying potential supporters. He managed to connect with his bread-and-butter issues of guns and gold, Murray said.

"He took out Laughlin pretty easily," Murray said, adding that Paul knew he was taking on the Republican establishment and delighted in it.

Murray said Paul's history with Gingrich actually goes back three decades when both were freshmen members in House. Gingrich was plotting a Republican takeover while Paul was an outspoken libertarian.

"Paul is in politics because he has a passion," Murray said, adding that Paul was never a foot soldier in Gingrich's army.

Murray contends that Paul is running a professional campaign with highly produced television ads. Paul was the first candidate to go negative on Gingrich, launching television ads attacking the former speaker for his inconsistencies and questionable conservative stances. Paul has also attacked Gingrich for expanding the size and scope of government through lobbying efforts.

Paul recently told ABC News' Jon Karl that Gingrich "may be the opposite of what I've been doing for 30 years. My positions haven't changed all that much."