President Bush has only exercised his veto power a few times, but today he sent a clear message to democrats.
He said he will not allow the latest stem cell research bill.
Mr. Bush said he vetoed the bill because it crosses a moral line and destroys human life.
Critics are outraged at the president.
Senator Hillary Clinton said the president puts ideology before science.
This is only the third time Bush has used his veto pen and one of the others was also concerning stem cell research.