The 50th anniversary of the passage of Medicare was celebrated with cake and a side of partisan politics.

Deep divisions between Democrats and Republicans over the popular program bubbled up this week in anticipation of Thursday's 50th anniversary of the creation of Medicare and Medicaid.

"Are we going to let Republicans cut Medicare-Medicaid benefits?" asked Rep. Jan Schakowsky, D-Ill., during a press conference Wednesday. "Are we going to let them [turn] Medicare into a voucher program or raise the age of eligibility?"

Schakowsky was among several Democrats who spoke about defending the popular entitlement program that provides healthcare for seniors.

"We must strengthen, not cut, voucher or block grant these essential pillars of economic security," said House Minority Leader Nancy Pelosi, D-Calif., referring to several Republican alternatives to reform Medicare that have been proposed over the years.

The event culminated in the lawmakers singing happy birthday to the programs while blowing out the candles on a cake.

Rep. Kevin Brady, R-Texas, struck a more worried tone while speaking at a National Journal event on Tuesday.

"Medicare just isn't set for the long term," said the chairman of the House Ways and Means Committee's health subcommittee. "The hospital trust will become insolvent in a short 15 years, and the demographics are just challenging."

Brady was referring to the projected insolvency of the hospital trust fund by 2030, which pays hospitals. However, the projections have been pushed back several times by the Medicare Board of Trustees, which once thought the fund would be insolvent in 2001.

He said that patients need more options and choices in Medicare than they have. Brady pointed to the success of the private Medicare Advantage plans.

Several Republican presidential candidates have brought up changes to Medicare.

Former Florida Gov. Jeb Bush recently walked back comments where he said he would "phase out" Medicare due to the program's coming financial struggles.

In a Tuesday campaign visit to New Hampshire, New Jersey Gov. Chris Christie said Medicare is the third rail of American politics.

"If you touch it you die," he said in a report in the Valley News newspaper. "So here's what we're going to do: We're going to hug it. We're not just going to touch it — we're going to hug it."

Republicans are worried about how the entitlement program can control the influx of new enrollees that comes from an aging population. About 19 million baby boomers will sign up for Medicare in the next decade or so, according to a government study on health spending.

But the Medicare program has been able to reduce costs over the years, according to a report from the nonpartisan Kaiser Family Foundation released Wednesday in the Journal for the American Medical Association.

The growth rate for Medicare spending was virtually flat in 2013 compared with a 6 percent growth between 2000 and 2008, the report said.

"Over the next decade, Medicare spending is projected to grow more slowly than private health insurance on a per capita basis — 3.4 percent from 2013 to 2023 vs. 4.8 percent for private insurance," the report noted.

Since Medicare is such a volatile election issue, it is not clear if any changes to Medicare will be made until after the 2016 election, the report said.

Despite the rhetoric on both sides, neither party has made a serious attempt to "broach the inevitable but difficult question of how the nation will finance medical care for an aging population," the report said.