Democratic challenger John Kerry on Monday broadened his attack on President George W. Bush to include stem cell research when he accused his rival of ignoring science that could offer millions of sick Americans a chance for a cure.

Campaigning in New Hampshire aside actor and activist Michael J. Fox, who has Parkinson’s disease, the Massachusetts senator said if elected he would remove Bush’s restrictions on using federal money for stem cell research and boost funding.

Stem cells are “master cells” that can give rise to various cells and tissues. Scientists believe that while the cells could lead to cures for conditions like Parkinson’s disease and spinal cord injuries, such advances would be years and perhaps decades away.

Citing ethical concerns, the Bush administration in 2001 sharply limited federal spending on research involving stem cells taken from human embryos.

“The hard truth is that when it comes to stem cell research, this president is making the wrong choice to sacrifice science for extreme right-wing ideology,” Kerry told a town hall meeting on science at a New Hampshire high school.

“President Bush just doesn’t get it. Faced with the facts, he just turns away,” Kerry said. “Time and again, he’s proven that he’s stubborn, out of touch, unwilling to change, unwilling to change course.”

Kerry’s campaign released a new television ad devoted to stem cell research that will air in battleground states. In the 30-second spot Kerry says it is time to lift political barriers to the research and that “millions of lives” are at stake.

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Bush campaign spokesman Steve Schmidt called Kerry’s attack “baseless” and “dishonest,” noting that there is no ban on stem cell research in America and that Bush was the first president to federally fund stem cell research - albeit confining it to a few dozen existing lines.

Kerry, however, noted that many of the stem cell lines available for federal research money have no scientific value or have been contaminated by mouse cells.

The attack came as a new poll by USA Today confirmed that Bush’s lead over Kerry had evaporated following last week’s candidates’ debate, the first of three face-offs between the two men. The poll showed the race in a dead heat with less than 30 days to go until the election.

Kerry has criticized Bush’s stem cell research policies before, but the latest attack appeared part of a larger effort by the Democrat to portray Bush as someone who stubbornly ignores facts both at home and abroad.

In Thursday’s debate, which opinion polls show Kerry won, the Democrat attacked the president’s stay-the-course resolve - a trait typically seen as one of Bush’s strengths.

As Bush said he would not wilt under pressure on foreign policy, Kerry noted that it was possible to be certain but also to be certain and wrong.