Julie Dawes -, Associated Press
Republican Mark Amodei answers a question on the economy as his fellow candidates Democrat Kate Marshall, Tim Fasano of the Independent American Party and Independent Helmuth Lehman (not pictured) wait to weigh in during a debate of candidates for 2nd Congressional District special election on Wednesday evening Aug. 17, 2011 in Reno, Nev. Most questions centered around the economy and jobs.

LAS VEGAS — Republican Mark Amodei is firing back at Democratic rival Kate Marshall in a pair of new TV ads that directly label the state treasurer a liar and a reckless investor of the public purse.

Amodei has largely avoided naming Marshall in previous ads, but the two spots released Thursday claim she lost Nevada money as state treasurer and has lied about Amodei's record on Medicare.

Amodei's campaign also announced Thursday that Republican presidential hopeful and former Massachusetts Gov. Mitt Romney had endorsed Amodei.

"Mark understands what is needed to bring jobs back to Nevada and get the country's economy back on track," Romney said in a statement.

Amodei and Marshall are competing in Nevada's Sept. 13 special election to fill a vacant U.S. House seat. The candidates engaged in the first debate of the campaign Wednesday night.

One of Amodei's new ads features his mother for the second time, signaling his campaign's hope that the elderly woman will warm voters' hearts. The ad features a snippet from a Marshall ad that showed Amodei praising a Republican plan to overhaul Medicare. Amodei has since said he does not support the plan but does support changes that will ensure Medicare's solvency in the future.

Amodei's mother is shown in his ad shaking her head as she watches Marshall's TV spot. She then says into the camera, "That's not true."

"Well said, Mrs. Amodei. Kate Marshall is still lying about your son," a narrator responds.

The second ad shows Marshall telling voters, "I'm in charge of your money." The ad goes on to state that Marshall is "just another politician reckless with your money."

Marshall has said that she protected Nevada's financial portfolio as best as she could as the markets have zigzagged in recent years.

"Even though these claims have been debunked by multiple, independent fact checks, Mark Amodei is still peddling his lies about Kate Marshall," said James Hallinan, Marshall's campaign spokesman, in a written statement.

Both campaigns are getting help from national leaders.

Former President Bill Clinton and Senate Majority Leader Harry Reid have urged voters to support Marshall.

Meanwhile, Republican House Speaker John Boehner is poised to lend Amodei a hand during a Reno fundraiser Friday morning, and Republican Sen. Dean Heller told The Associated Press he wants Amodei to replace him in the House.

"We need a lot more Mark Amodeis than we need Kate Marshalls," Heller said.

Heller was elected to represent northern Nevada in the House in 2006. He was appointed to the Senate in May after Republican Sen. John Ensign resigned over a sex scandal.

The endorsement does not come as a surprise. Heller has helped Amodei raise cash in Washington and is eager to burnish his conservative credentials before the 2012 Senate race, when he will face Democratic Rep. Shelley Berkley of Las Vegas.

A regular election for the House seat will be held in November 2012.