VIRGINIA EWERS is angry at the Republican Party she has long supported. A widow with a history of poor health, Ms. Ewers lives in subsidized housing for the elderly on a monthly income of $524 in Social Security and veteran's pension payments. A plan drafted by Republicans would nearly double her monthly Medicare premiums. ''I would have to give up everything else I have, which is very little,'' she says, sitting in the ornate Westward Ho, a home for low-income elderly. ''I am a Republican, but the way [they] have been handling this, I could change my party real easily right now.'' She is not alone. The GOP proposal to scale back the rate of increase in Medicare spending to reduce the federal deficit has provoked anger, concern, and confusion among senior citizens in Arizona. In the public-relations battle for the hearts and minds of the elderly, neither side appears to be winning a quick and sure victory. But Republicans are clearly suffering more casualties, especially among lower-and middle-income elderly. How the plan resonates among senior citizens - traditionally an important Republican constituency - will be important for 1996. Mindful of the implications, both parties are launching one of the most concerted PR campaigns since the great health-care debate - including trotting out Hollywood celebrities for on-air pitches. Arizona offers a window into how the messages are playing. For now, it doesn't look good for the GOP, even though this is a state that launched the national conservative movement in 1964 with the unsuccessful presidential bid of Barry Goldwater, still an icon here. Under the plan outlined last week by House Speaker Newt Gingrich (R), seniors would pay monthly premiums of $90 to $93 by 2002. President Clinton's budget calls for monthly payments of $83 by then. The current premium is $46.10. Dinner table talk At the Beatitudes Campus of Care, a collegiate-type setting where 700 retired teachers, ministers, and other middle-income professionals live, conversation this week over beef stroganoff in the facility's cafeteria reflects the residents' anxiety. Mary Lemke, a former school principal from Brea, Calif.,says that an increase would mean, ''I go that much farther behind. There's nothing I can cut. I have already done that.'' Mae June Piazza, who worked for the Arizona Department of Insurance, follows the issue through magazines and newspaper editorials. She supports Republicans' push for less government and restrained spending. But ''as far as knowing what the changes will be, it's hard to know because one politician says this may happen, while another says something else may happen,'' Ms. Piazza says. Even Clinton may be backpedaling on his plan. He told a Jacksonville, Fla., audience this week that he may accept Medicare cutbacks that make affluent older Americans pay more. Political pollster Earl de Berge said the attitudes expressed today by the elderly have been developing for the last three years. ''The main issue is whether in the long run it will make the elderly scratch their heads and think twice before voting Republican,'' Mr. De Berge says. ''There is a lot less willingness on the part of the elderly to give automatic credence to the GOP on this issue.'' But in Sun City West, Ariz., an affluent retirement community an hour's drive from Phoenix, Ed Cirillo says Republicans have made a persuasive case for cutting costs to the health-care program. Accusing Democrats of ''scare tactics,'' Mr. Cirillo says his neighbors are ''fed up and want Washington to be shrunk and power returned to the states.'' Arizona, a retirement mecca for the elderly with its dry climate and mild winters, has a sizable senior-citizen population. About 350,000 people age 60 and over live in Phoenix's Maricopa County. About 9 percent live at or below the poverty level. The hardest hit Peggy Brown, who also lives at the Westward Ho - once a landmark hotel - is one of the elderly poor. She lives on $478 a month, with the state's program for the medically indigent paying her Medicare premiums. While not a fan of either party's proposal to raise Medicare premiums, she finds the Democrats' plan more palatable, saying,'' You are going to have to vote for one, so you vote for the lesser one.'' An avid viewer of C-SPAN and CNN, she feels that politicians are out of touch with her concerns and wishes they could swap places with her for just a month. ''I'd like to live with some kind of dignity left,'' she says.