Instead, the Republicans want to raise revenues by eliminating deductions and raise the age for Medicare coverage by a couple of years. This really makes no sense to me. Raising revenue (taxes) is still raising taxes, whether it is done by raising the top rate or by eliminating deductions. Are they just playing a semantics game? No. They know they raising the top rate will affect only the wealthy, while eliminating deductions would easily include many of the middle class -- thus limiting the amount of extra tax the wealthy will have to pay.
The problem though is that while Wall Street loves the GOP idea of raising revenue, the GOP's base voters aren't so crazy about the idea. Only 39% approve of the idea (even less than among Independents and Democrats). And those same base Republican voters don't much like the idea of raising the age to qualify for Medicare either. Only 30% approve of that silly idea.
This puts the Republicans in a very delicate position. While refusing to raise the top tax rate will probably hurt them in the next general election, the other two ideas (eliminating deductions and raising the age for Medicare) could cause them problems in the GOP primary. If they continue to support these ideas, they will keep the money flowing from Wall Street but could lose votes in the primary. If they abandon these ideas, they will make the base happy but could lose funds from the Wall Street moneymen.
This may all be a moot point though. If they continue to oppose cutting taxes for the bottom 98%, it may not matter whether they survive a Republican primary or not (because they may have made it impossible for any but those in the very safest GOP districts to win in the general election). It is just not a good time to be a Republican in Congress.