Democratic Senatorial Campaign Committee Chairwoman Patty Murray predicted Thursday that her party would maintain control of the Senate in 2012, attributing that optimism to President Barack Obama’s position at the top of the ticket and her view that the “extreme” Republican-led House is sending independent voters fleeing from the GOP.

The Democrats are defending 23 seats to the Republicans’ nine and working with a Senate map that remains dramatically tilted toward the GOP. But the Washington state Democrat argued that public reaction to the House Republican budget plan for fiscal 2012 was a political boon for Democratic Senate candidates, while insisting that her vulnerable incumbents running in GOP-leaning states were laying the foundation to survive tough challenges. Republicans need to flip just four seats to win control of the Senate.

“I’m seeing a changing landscape,” Murray said. “People are seeing what [the Republicans] stand for.”

Murray sidestepped questions of Democratic vulnerability in states where Obama is weak and the Democratic incumbents’ approval ratings are equally troubling. She maintained that Democratic Senators such as Claire McCaskill (Mo.), Ben Nelson (Neb.), Bill Nelson (Fla.) and Jon Tester (Mont.) are raising money and defining their opponents — or likely opponents, in the cases where the GOP is sorting out its primary field — in a manner that puts them in a strong position to win re-election.

Murray said Democratic incumbents raised a collective $20 million in the first quarter of this year and added that she expects most if not all of them to forgo retirement and seek re-election.

The DSCC chairwoman said she is targeting the GOP-held seats in Arizona, Indiana, Maine, Massachusetts, Nevada and Texas in what she referred to as her “Six in ’12” campaign. “I am aggressively going after Republican seats,” said Murray, the fourth-ranking Senate Democrat who is in her second tour of duty at the DSCC.

The National Republican Senatorial Committee mocked Murray’s view of the political climate and described her optimism as unfounded while rebutting claims that the House GOP push to eliminate funding for Planned Parenthood in the fiscal 2011 continuing resolution has buoyed the Democrats’ political prospects.

The NRSC indicated that Senate Republicans are happy to run on the House GOP fiscal 2012 budget plan and against an Obama counterproposal that includes tax hikes on higher earners and some small businesses and less in deficit reduction than offered by the GOP. The Republican budget would overhaul Medicare and Medicaid, affecting only those Americans under 55.

NRSC spokesman Brian Walsh said in a statement that national Democrats “appear oblivious to the reality that a number of their incumbents are running in red states next year” and charged that “extreme” rhetoric from the DSCC “leaves their party even more vulnerable to losing control of the Senate next year.”