"Upper Middle Class" is a very broad term. If you mean those making around $90,000 - $150,000 (A Common Definition), then it all depends on what tax. I believe that the gas tax should be raised, which is technically raising taxes on the upper middle class. The income tax? Likely not. I think that systematic tax reform is needed, and shouldn't involve raising taxes on these folks.
In the end, I think that a promise to "never raise taxes on the middle class, nor anyone" is stupid and impractical, but I believe that we should make an attempt to lower the cost of living for these (and especially those with lesser income) folks, through decreasing the price of healthcare, making energy more affordable and greener, and through establishing childcare as a universal right.
1. No it is not
technically - it is
effectively.
2. Those making >$100,000 a year
are the top one percent in Arkansas.