(Updates with Clinton, Obama quotes; changes dateline from Lebanon, Pa.)

By Jeff Mason

BETHLEHEM, Pa., April 20 (Reuters) - With two days to go before a crucial U.S. presidential vote, Democrats Barack Obama and Hillary Clinton campaigned through Pennsylvania on Sunday as the former first lady got the support of one of her fiercest critics.

Tuesday's primary to help pick the Democratic candidate against Republican John McCain in November's presidential election is the first contest in six weeks and has become a major test in the race to the party's nomination.

Clinton, a New York senator, leads in state polls but Obama, an Illinois senator, has cut into her one-time double-digit lead in recent weeks.

With less than 48 hours to go before the polls open, the two campaigned vigorously around the state, both claiming the other was conducting a negative campaign.

At a town hall meeting in Reading, Obama said Clinton believed in "the say-anything, do-anything, special interest-driven politics of Washington -- that that's how it's got to be, that that's how the game is played."

"So you should elect her to be your nominee because she's been in Washington longer and she knows how to play the game better," he said, adding he was a different candidate who would find a common ground.

But at a rally in Bethlehem, Clinton said it was Obama who had gone negative since their Philadelphia debate last week.