All of Bush's proposals so far are bad. His economic plutocrats will not permit any good ones because raising taxes is by definition bad. They claim it would not be good for the economy. The real reason is that it would cost them some money.
Nevertheless, consider this. The upper limit on incomes subject to payroll taxes today is $90,000. In 1981, 90 percent of the total income earned in wages and salaries was subject to the payroll tax. Income has shifted to those with higher incomes. The result is that only 85% of such income is liable to the the payroll tax today. Hiking the level to 90% again would require that the upper limits would have to be $138,000. This would take care of about 1/3 of the 75-year gap between tax revenues and benefit payments. See the February 18, 2005 edition of The Christian Science Monitor. See: http://www.csmonitor.com/2005/0218/p01s01-uspo.html
Removing the cap altogether would completely do even more. Why should there be a cap? Low income people pay on all their earnings. Rich folks should too.
We also need a wealth tax and to preserve the estate tax. Finally, we need to roll back the massive tax cuts for the rich that are already sending the deficit soaring out of sight. The justification for raising taxes on wealth and high incomes is simple. The production of income and wealth is a social process. No one can earn money without the functioning of an economic system that requires everyone -- those who clean the bathrooms and the offices of the rich -- as well as the talent and hard work of rich people. The notion that market forces distribute income and wealth in accordance with justice or rationality is absurd, a myth. Consider the fact, e. g., that professional athletes who earn 10 million dollars a year would gladly play for 5 or 2 million, if that is all they could get. Most of them could not earn nearly that much apart from their athletic skills. Nobel prize winning economists could make the case technically for everything I have said. It is ideology and selfish interest that are at the base of the rejection of such ideas, not economic fact or logic.