Candidates seeking to challenge Illinois U.S. Senator Dick Durbin can begin filing their nominating petitions Monday. But would-be Republican opponents were not waiting to go after the veteran Democrat.

Any of the GOP contenders will face an uphill race against the entrenched incumbent. Durbin was last re-elected in a 2008 landslide over little-known Republican Steve Sauerberg.

Durbin has close ties to President Barack Obama. The No. 2 Democrat in the Senate, Durbin is a steadfast backer of Obama’s agenda.

“I hope my experience in Washington…the seniority that I have, can make me a more effective senator to help this state,” Durbin told WBEZ Friday.

Durbin also enjoys wide name recognition in Illinois, and had more than $4.8 million in his campaign coffers as of the end of September, according to federal campaign finance records.

But candidates vying for the GOP nod in the March 18 primary hope to capitalize on the bungled rollout of the Affordable Care Act, often called “Obamacare,” and are already criticizing Durbin for his long career in Washington.

“I think a lotta people are like me — tired of professional politicians,” said 43-year-old Doug Truax, a healthcare consultant from west suburban Downers Grove who is making his first run at public office. “And it’s time for somebody like Dick Durbin to take a break. I mean he’s been in [Congress] since ‘82. I was 12 when he first got elected.”

Republican state Sen. Jim Oberweis, who owns the dairy company that bears his name, is also tossing his hat into the ring, after having just been elected to the General Assembly last year.

Some Republican leaders have reportedly expressed concerns about Oberweis’ candidacy, given his electoral track record. He’s staged several unsuccessful bids for public office. And he has come under fire in the past for comments he made about “illegal aliens” in a 2004 campaign ad, and a remark in 2001 in which he likened abortion opponents to the Taliban.

Oberweis once again apologized for those remarks in his official video announcing his bid to take on Durbin. While calling it an “uphill battle” to beat Durbin in the general election, Oberweis said he was not too concerned about winning the GOP primary.

“None of the other candidates have ever run statewide,” Oberweis said. “None of the other candidates have been elected. And none of the other candidates have the financial backing and resources necessary to mount a serious campaign against Dick Durbin.”

Oberweis said there is “no question” that he will be a “significant contributor” to his own campaign, though he did not specify how much he is willing to spend. Federal law allows U.S. Senate candidates to spend unlimited amounts of their own money to get themselves elected.

But that did not seem to faze Durbin.

“I’m just in the category of mere mortal, when it comes to the money that I can put into a race,” he said. “But if it comes down to who can buy this seat or pay the most for it, I probably won’t win it. But I think it comes down to something more important. That is, the people [of] this state have to make a decision on whom they trust.”

Alex Keefe is political reporter at WBEZ. You can follow him on Twitter and Google+.