BOSTON (AP) — Massachusetts Democrats are trying to tie Republican U.S. Sen. Scott Brown to Mitt Romney's hand-picked running mate, conservative Wisconsin congressman Paul Ryan, in this year's hotly contested Senate race.

Democrats are banking that Ryan's budget proposals, including his plans to transform Medicare into a voucher system and re-shape the nation's tax system, could undermine support for Brown and other Massachusetts Republicans, including congressional hopeful Richard Tisei.

Republicans are pushing back, trying to portray Brown's Democratic challenger Elizabeth Warren as a free-spending liberal who supports higher taxes

Brown has endorsed Romney, but also voted against Ryan's budget plan twice, saying he couldn't support Ryan's Medicare proposal.

Warren argues that the choice of Ryan shows Republicans "are racing in the wrong direction."

"Scott Brown and the Republicans are doubling down on policies that will hurt seniors, make it tougher for families to educate their children, and leave small businesses struggling," Warren said in a statement Monday. "The Republican vision of the future is tax breaks for billionaires and repeal of reforms for Wall Street."

Asked for comment on Romney's choice of Ryan and if there are any major areas where Brown and Ryan disagree, a spokeswoman for Brown said it's Warren who wants to gut Medicare in order to help pay for federal health care initiatives.

"She supports cutting more than $700 billion dollars from current Medicare beneficiaries and raising Medicare taxes by $317 billion in order to pay for the new federal health care bill," Brown spokeswoman Alleigh Marre said in a statement. "That's wrong. Scott Brown believes we shouldn't make changes to Medicare that affect current seniors."

Warren said Brown is "just flat wrong," and that the 2010 health care law puts Medicare on a more solid footing.

Romney tapped Ryan on Saturday as his choice for vice president on the Republican presidential ticket.

The former Massachusetts governor has defended Ryan's proposals for Medicare, telling Florida voters that the Republican ticket wants to "make sure that we preserve and protect Medicare."

Ryan's proposal would turn steer future retirees into private insurance plans, with a fixed payment from the government that may or may not cover as much of a retiree's costs as does the current program. Ryan, chairman of the House Budget Committee, would also turn Medicaid over to the states and sharply limit the growth of future spending on the safety net program.

Democrats also seized on Romney's choice of Ryan in Massachusetts' closely-watched 6th Congressional District race pitting incumbent Democrat John Tierney against Republican challenger Richard Tisei.

In a conference call with reporters on Monday, Tierney tried to tie Tisei to Ryan's proposal, saying the plan would also cut funding for renewable energy projects, roads and bridge construction, and education.

"If elected, his first vote would be for those people who would implement that plan," Tierney said.

Tisei praised Ryan as "a serious politician who sees our country's economic problems in clear terms" and called his plan "a good starting point for discussion," but said the two don't agree on every issue.

"We need problem solvers who look beyond party and who are willing to step up to the plate and lead," Tisei said in a statement. "I hope to be that congressman and it is my hope that Congressman Ryan and Mitt Romney will also be such leaders."

Massachusetts Gov. Deval Patrick, the state's top Democrat, also faulted Ryan's plan, saying it would "decimate education funding and end Medicare."

On Monday, both parties released new web videos aimed at the other party's Senate candidate.

The Massachusetts Republican Party launched a video highlighting what they said was Warren's support for "radical tax hikes" that would cost trillions over the next decade, while the Massachusetts Democratic Party released a video of old clips of Brown praising Romney and Ryan.