Senate Republicans have introduced a plan that would create a Roth 401(k) and would create more protections for workers' pensions when companies convert to cash balance plans. Retirement savings has suddenly become a major campaign issue, and the package is broad-based enough that it may make it through Congress, say observers. It would raise some contribution limits for retirement-savings accounts and offer a new tax credit to encourage low- and moderate-income savers. Critics contend that most of the provisions will only benefit upper-income earners, and administration officials say the package needs some improvement.