When you give three options, as CBS did, a large number of people will opt for the comfortable middle option. In short, it depends how you frame the debate. Something the politicians have known forever.
A couple factors at play....
First is wording..... Rasmussen linked raising the debt ceiling with tax increases (no mention of spending cuts), while CBS links spending cuts and tax increases together to raise the ceiling.
Even cbs could find only 3% who want only tax increases (ie 97% want some spending cuts and of that 97%, most would like some new revenue into the package as well)
There is also the partisan balance int he poll. - I forget Rasmussens current weightings but the number of GOP and Dems is pretty close.
CBS, by contrast, has a few more democrats in the mix..
Total Republicans (24%)
Total Democrats (35%)
Total Independents (41%)
This slides the poll several % in the tax hike direction as well.