Using extraordinary language even for a heated political campaign, Sen. Ken Salazar denounced Rep. Marilyn Musgrave Wednesday as "one of the agents of hate" who "should be ashamed of herself."

Salazar's denunciation came after Musgrave released a new campaign ad against Democratic challenger Betsy Markey, saying that Markey faces possible prison time for improprieties while serving as Salazar's aide from 2005 to 2007.

"I think these campaign ads for her have reached a new low in Colorado politics," Salazar said in a conference call with reporters. "Congresswoman Musgrave should be ashamed of herself and the voters of the 4th Congressional District should be appalled by her blatant disregard for the truth."

Jason Thielman, Musgrave's campaign manager, dismissed Salazar's criticism as a "side show, Betsy Markey has serious questions that need to be answered."

Musgrave, a three-term Republican incumbent, has frequently cited her work with Salazar as an example of how well she works with Democrats. She featured a picture of herself with the Democratic senator in her first campaign ad this year.

"Marilyn won't let Salazar's inflamed rhetoric interfere with our ability to work with him on important issues like Rocky Mountain National Park, stopping a proposed uranium mine or solving our economic crisis when she returns to Congress in November," Thielman said.

Democratic Gov. Bill Ritter also criticized Musgrave's ad, though in less strident language than Salazar.

"I'm disappointed in Congresswoman Musgrave's dishonest campaign ads. I've known Betsy Markey for years. Betsy is above reproach and has always conducted herself with the highest level of integrity," Ritter said.

Musgrave's new ad opens with a voice-over that says, "Like the worst on Wall Street, Betsy Markey gamed the system and got rich on taxpayer money. But Millionaire Markey got caught."

The ad continues, "The Justice Department has been asked to investigate whether Markey broke the law" and said she could face five years in prison. The ad fails to mention that the investigation request came from the Republican Party chairman in the 4th Congressional District.

Musgrave's campaign has focused almost exclusively in the past month on Markey's family business, Syscom Services, which gets about a quarter of its revenue from federal contracts for computer software and services.

Musgrave initially alleged that Markey used her position as an aide to Salazar to steer contracts to Syscom but quickly dropped that approach to focus on inconsistencies in Markey's statements about her role in the company.

Ronald Buxman, chairman of the 4th Congressional District Republican Party, sent letters requesting an investigation of Syscom to the Justice Department, General Services Administration and Small Business Administration.

He asked the agencies to look into whether Syscom falsely represented itself as a woman-owned company to obtain government contracts and whether federal purchasing agents violated a law that prohibits them from knowingly awarding contracts to a company owned or substantially owned by a federal employee.

Markey has repeatedly denied the allegations and said Musgrave has produced no evidence to back them up. She said the Musgrave campaign sent the letter to the Justice Department and other federal agencies "so they could use it in an ad, saying that I'm under investigation."

"Several weeks ago these allegations were made by the Musgrave campaign and they said that it was up to me to disprove them, and I have done that," Markey said.

"And I believe that Marilyn Musgrave needs to apologize to my family. She needs to apologize to Senator Salazar and all of the employees of Syscom Services."

Thielman said: "Betsy has lied to the public. She has filed false documents with the government and engaged in business practices that pose a conflict of interest. Just because she is rich and well connected doesn't remove her from the consequences that any other citizen would face for similar misdealing."

Colorado State University political scientist John Straayer said Musgrave's latest ad could boomerang on her. "Might we conclude that linking Syscom to Wall Street to five years in prison is intimating, if not stating directly, that Markey is a felon?" Straayer said. "If this doesn't backfire, there really is a pathology infecting our democracy."

Salazar said voters have a clear choice in the 4th Congressional District.

"On the one hand, they have somebody who is clean as a whistle in the name of Betsy Markey, who's been a successful business owner, someone who has been civically engaged in her community, who knows Fort Collins, Greeley and the Eastern Plains well.

"And on the other hand they have someone in the name of Marilyn Musgrave, who has been one of the agents of hate, and political division for her term in the U.S. Congress."

When asked for a reaction to Salazar's criticism, Thielman responded with a press release stating that Markey's brother may have helped steer contracts to her company while he worked at the Department of Labor.

The Musgrave campaign provided no evidence that Thomas Markey influenced contract awards, saying only that he worked in the 17,000-employee federal agency during a four-year period when his sister's company got $500,000 in contracts from the Department of Labor.

Markey spokesman Ben Marter said the new allegation left him "speechless."

Thielman said Syscom got contracts totaling $500,000 between 1997 and 2001 from the Bureau of Labor Statistics and the Employment and Training Administration, agencies of the Labor Department. Records available on the Internet show that Thomas Markey didn't work for those agencies during that time but was a senior administrator in other Labor Department agencies.

The Northern Colorado congressional race has been among the most closely watched in the country in the past few weeks. Republicans have held the seat for 35 years, and Democrats believe they have an opportunity to pick up the seat and expand their House majority.

The race has become increasingly negative as national Democratic and Republican party groups this week launched their own ad campaigns attacking the other party's nominee. Musgrave has already been hit with almost $2 million in attack advertising by independent groups.