As lawmakers wrestle with how to pay for a proposed healthcare system overhaul, an emerging flashpoint of debate is whether higher-income employees should face steeper taxes on health benefits than those with more-modest income. The greatest chance for bipartisan accord, for now, is in the hands of two Senate players: Finance Chairman Max Baucus and his Republican counterpart, Sen. Charles Grassley of Iowa. Baucus favors taxing some employer-provided health benefits. But congressional Democrats and Republicans may have difficulty finding common ground on how to limit the tax benefits that currently favor employer-based health plans.